Books: vollständiger Offline-Modus für EPUB-Reader

- IndexedDB v2 mit zwei neuen Stores: book_meta (Buchliste +
  Lesefortschritt) und book_annotations (Lesezeichen & Highlights)
- loadBookList fällt bei Netzwerkfehler auf lokalen Meta-Cache zurück,
  blendet Upload-Zone aus und zeigt Offline-Hinweis
- Leseposition (scroll_fraction + position_anchor) wird bei jedem
  Auto-Save lokal gecacht, sodass offline-Öffnen am richtigen Ort
  landet
- Lesezeichen und Highlights werden nach Server-Abruf lokal gecacht
  und bei Netzwerkfehler von dort geladen; Änderungen offline bleiben
  bis zur nächsten Synchronisierung erhalten
- Mobile Reader-Header: kompaktere Abstände, Fortschritts-Input auf
  kleinen Screens ausgeblendet

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -33,3 +33,6 @@ CLAUDE.md
 # OS
 .DS_Store
 Thumbs.db
+antennapod-feeds-2026-03-19.opml
+.gitignore
+playlist.m3u

static/css/app.css

@@ -1439,6 +1439,13 @@ body.dnd-mode .timer-display {
   .podcast-thumb-lg { width: 60px; height: 60px; }
   .podcast-feed-actions { flex-direction: column; }
   .episode-actions { flex-direction: column; }
+
+  /* Reader auf Mobile: Header kompakter, Fortschrittsfeld versteckt */
+  .reader-header { padding: 6px 8px; gap: 4px; }
+  .reader-title { font-size: 13px; }
+  .reader-header-actions { gap: 4px; }
+  .reader-progress-wrap { display: none; }
+  .reader-content { padding: 16px 10px; }
 }
 
 /* =========================================================
@@ -1473,6 +1480,12 @@ body.dnd-mode .timer-display {
   padding: 24px 0 16px;
 }
 
+.offline-notice {
+  font-size: 13px;
+  color: var(--accent);
+  padding: 4px 0 8px;
+}
+
 .book-key-bar {
   display: flex;
   align-items: center;

static/js/app.js

@@ -2690,12 +2690,22 @@ function restoreFromAnchor(contentEl, anchor) {
 // Book cache — IndexedDB, evict after 4 weeks of inactivity
 // ---------------------------------------------------------------------------
 const _BOOK_CACHE_STORE       = 'books';
+const _BOOK_META_STORE        = 'book_meta';
+const _BOOK_ANNOTATIONS_STORE = 'book_annotations';
 const _BOOK_CACHE_EVICT_MS    = 4 * 7 * 24 * 60 * 60 * 1000;
 
 function _openBookCacheDb() {
   return new Promise((resolve, reject) => {
-    const req = indexedDB.open('diora_book_cache', 1);
-    req.onupgradeneeded = e => e.target.result.createObjectStore(_BOOK_CACHE_STORE, {keyPath: 'id'});
+    const req = indexedDB.open('diora_book_cache', 2);
+    req.onupgradeneeded = e => {
+      const db = e.target.result;
+      if (!db.objectStoreNames.contains(_BOOK_CACHE_STORE))
+        db.createObjectStore(_BOOK_CACHE_STORE, {keyPath: 'id'});
+      if (!db.objectStoreNames.contains(_BOOK_META_STORE))
+        db.createObjectStore(_BOOK_META_STORE, {keyPath: 'id'});
+      if (!db.objectStoreNames.contains(_BOOK_ANNOTATIONS_STORE))
+        db.createObjectStore(_BOOK_ANNOTATIONS_STORE, {keyPath: 'id'});
+    };
     req.onsuccess  = e => resolve(e.target.result);
     req.onerror    = ()  => reject();
   });
@@ -2757,6 +2767,82 @@ async function _evictBookCache(bookList) {
   } catch {}
 }
 
+async function _saveBookMeta(books) {
+  try {
+    const db = await _openBookCacheDb();
+    const ids = new Set(books.map(b => String(b.id)));
+    await new Promise(resolve => {
+      const tx = db.transaction(_BOOK_META_STORE, 'readwrite');
+      const store = tx.objectStore(_BOOK_META_STORE);
+      for (const b of books) store.put(b);
+      store.openCursor().onsuccess = e => {
+        const cursor = e.target.result;
+        if (!cursor) return;
+        if (!ids.has(String(cursor.value.id))) cursor.delete();
+        cursor.continue();
+      };
+      tx.oncomplete = resolve;
+      tx.onerror    = resolve;
+    });
+  } catch {}
+}
+
+async function _loadCachedBookMeta() {
+  try {
+    const db = await _openBookCacheDb();
+    return await new Promise(resolve => {
+      const req = db.transaction(_BOOK_META_STORE).objectStore(_BOOK_META_STORE).getAll();
+      req.onsuccess = e => resolve(e.target.result || []);
+      req.onerror   = ()  => resolve([]);
+    });
+  } catch { return []; }
+}
+
+async function _updateCachedBookProgress(bookId, fraction, anchor) {
+  try {
+    const db = await _openBookCacheDb();
+    await new Promise(resolve => {
+      const tx = db.transaction(_BOOK_META_STORE, 'readwrite');
+      const store = tx.objectStore(_BOOK_META_STORE);
+      const req = store.get(bookId);
+      req.onsuccess = e => {
+        const entry = e.target.result;
+        if (entry) {
+          entry.scroll_fraction  = fraction;
+          entry.position_anchor  = anchor;
+          entry.last_read        = new Date().toISOString();
+          store.put(entry);
+        }
+      };
+      tx.oncomplete = resolve;
+      tx.onerror    = resolve;
+    });
+  } catch {}
+}
+
+async function _saveAnnotationsCache(bookId, type, ct, iv) {
+  try {
+    const db = await _openBookCacheDb();
+    await new Promise(resolve => {
+      const tx = db.transaction(_BOOK_ANNOTATIONS_STORE, 'readwrite');
+      tx.objectStore(_BOOK_ANNOTATIONS_STORE).put({id: `${bookId}_${type}`, ct, iv});
+      tx.oncomplete = resolve;
+      tx.onerror    = resolve;
+    });
+  } catch {}
+}
+
+async function _loadAnnotationsCache(bookId, type) {
+  try {
+    const db = await _openBookCacheDb();
+    return await new Promise(resolve => {
+      const req = db.transaction(_BOOK_ANNOTATIONS_STORE).objectStore(_BOOK_ANNOTATIONS_STORE).get(`${bookId}_${type}`);
+      req.onsuccess = e => resolve(e.target.result || null);
+      req.onerror   = ()  => resolve(null);
+    });
+  } catch { return null; }
+}
+
 // Reader settings
 let readerSettings = { fontSize: 16, lineHeight: 1.8, maxWidth: 65, theme: 'dark',
                         fontFamily: 'serif', noBold: false,
@@ -2836,10 +2922,10 @@ async function loadBookList() {
         const metaBuf = await decryptBytes(key, b.meta_iv, b.meta_ct);
         const meta = JSON.parse(new TextDecoder().decode(metaBuf));
         bookMetaCache[b.id] = {title: meta.title || '?', author: meta.author || '', type: meta.type || 'epub'};
-        decrypted.push({id: b.id, title: meta.title || '?', author: meta.author || '', type: meta.type || 'epub', scroll_fraction: b.scroll_fraction, uploaded_at: b.uploaded_at, last_read: b.last_read || null, keyOk: true});
+        decrypted.push({id: b.id, title: meta.title || '?', author: meta.author || '', type: meta.type || 'epub', scroll_fraction: b.scroll_fraction, position_anchor: b.position_anchor || '', uploaded_at: b.uploaded_at, last_read: b.last_read || null, keyOk: true});
       } catch (e) {
         bookMetaCache[b.id] = {title: `Book #${b.id}`, author: '', type: 'epub'};
-        decrypted.push({id: b.id, title: `Book #${b.id}`, author: '', type: 'epub', scroll_fraction: b.scroll_fraction, uploaded_at: b.uploaded_at, last_read: b.last_read || null, keyOk: false});
+        decrypted.push({id: b.id, title: `Book #${b.id}`, author: '', type: 'epub', scroll_fraction: b.scroll_fraction, position_anchor: b.position_anchor || '', uploaded_at: b.uploaded_at, last_read: b.last_read || null, keyOk: false});
       }
     }
     decrypted.sort((a, b) => {
@@ -2848,11 +2934,31 @@ async function loadBookList() {
       if (b.last_read) return 1;
       return b.uploaded_at.localeCompare(a.uploaded_at);
     });
+    _saveBookMeta(decrypted); // persist for offline
     renderBookList(decrypted);
   } catch (e) {
+    // Network error — try offline fallback
+    const cachedBooks = await _loadCachedBookMeta();
+    if (cachedBooks.length) {
+      cachedBooks.sort((a, b) => {
+        if (a.last_read && b.last_read) return b.last_read.localeCompare(a.last_read);
+        if (a.last_read) return -1;
+        if (b.last_read) return 1;
+        return (b.uploaded_at || '').localeCompare(a.uploaded_at || '');
+      });
+      for (const b of cachedBooks) bookMetaCache[b.id] = {title: b.title, author: b.author, type: b.type || 'epub'};
+      const uploadArea = $('book-upload-area');
+      if (uploadArea) uploadArea.style.display = 'none';
+      renderBookList(cachedBooks);
+      const notice = document.createElement('p');
+      notice.className = 'muted offline-notice';
+      notice.textContent = 'Offline — gespeicherte Bücher. Fortschritt wird beim nächsten Öffnen synchronisiert.';
+      listEl.prepend(notice);
+    } else {
       if (listEl) listEl.innerHTML = `<p class="muted">Error loading books: ${e.message}</p>`;
     }
   }
+}
 
 const _brokenBooks = new Set();
 
@@ -3380,12 +3486,21 @@ async function openBook(bookId) {
     }
 
     // Restore scroll position — must happen BEFORE auto-save timer is started
+    try {
+      let fraction = 0, anchor = '';
       try {
         const progressRes = await fetch('/books/');
         const allBooks = await progressRes.json();
         const bookData = allBooks.find(b => b.id === bookId);
-      const fraction = bookData ? (bookData.scroll_fraction || 0) : 0;
-      const anchor = bookData ? (bookData.position_anchor || '') : '';
+        fraction = bookData ? (bookData.scroll_fraction || 0) : 0;
+        anchor   = bookData ? (bookData.position_anchor || '') : '';
+      } catch {
+        // offline — use cached meta
+        const cached = await _loadCachedBookMeta();
+        const bookData = cached.find(b => b.id === bookId);
+        fraction = bookData ? (bookData.scroll_fraction || 0) : 0;
+        anchor   = bookData ? (bookData.position_anchor || '') : '';
+      }
       _currentPositionAnchor = anchor;
       if (isPdf && readerSettings.pdfPaginated) {
         if (fraction > 0 && pdfTotalPages > 1)
@@ -3532,6 +3647,9 @@ async function saveReaderProgress() {
     _currentPositionAnchor = anchor;
   }
 
+  // Always update local cache so offline re-opens land at the right position
+  _updateCachedBookProgress(currentBookId, fraction, anchor);
+
   // Cache for sendBeacon on unload
   _lastProgressBeacon = {
     url: `/books/${currentBookId}/progress/`,
@@ -4117,6 +4235,7 @@ async function loadBookmarks(bookId) {
     const res = await fetch(`/books/${bookId}/bookmarks/`);
     const {ct, iv} = await res.json();
     if (ct) {
+      _saveAnnotationsCache(bookId, 'bookmarks', ct, iv); // persist for offline
       const key = await getOrCreateEncKey();
       const plain = await decryptBytes(key, iv, ct);
       currentBookmarks = JSON.parse(new TextDecoder().decode(plain));
@@ -4124,9 +4243,19 @@ async function loadBookmarks(bookId) {
       currentBookmarks = [];
     }
   } catch (e) {
+    // offline fallback
+    const cached = await _loadAnnotationsCache(bookId, 'bookmarks');
+    if (cached?.ct) {
+      try {
+        const key = await getOrCreateEncKey();
+        const plain = await decryptBytes(key, cached.iv, cached.ct);
+        currentBookmarks = JSON.parse(new TextDecoder().decode(plain));
+      } catch { currentBookmarks = []; }
+    } else {
       currentBookmarks = [];
     }
   }
+}
 
 async function saveBookmarks() {
   if (!currentBookId) return;
@@ -4137,6 +4266,7 @@ async function saveBookmarks() {
     const body = JSON.stringify({ct: ciphertext, iv});
     const url = `/books/${currentBookId}/bookmarks/`;
     _lastBookmarkBeacon = {url, body};
+    _saveAnnotationsCache(currentBookId, 'bookmarks', ciphertext, iv); // keep local cache current
     await fetch(url, {
       method: 'POST',
       headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},
@@ -4435,6 +4565,7 @@ async function loadHighlights(bookId) {
     const res = await fetch(`/books/${bookId}/highlights/`);
     const {ct, iv} = await res.json();
     if (ct) {
+      _saveAnnotationsCache(bookId, 'highlights', ct, iv); // persist for offline
       const key = await getOrCreateEncKey();
       const plain = await decryptBytes(key, iv, ct);
       currentHighlights = JSON.parse(new TextDecoder().decode(plain));
@@ -4443,8 +4574,19 @@ async function loadHighlights(bookId) {
     }
     applyHighlightsToContent();
   } catch (e) {
+    // offline fallback
+    const cached = await _loadAnnotationsCache(bookId, 'highlights');
+    if (cached?.ct) {
+      try {
+        const key = await getOrCreateEncKey();
+        const plain = await decryptBytes(key, cached.iv, cached.ct);
+        currentHighlights = JSON.parse(new TextDecoder().decode(plain));
+      } catch { currentHighlights = []; }
+    } else {
       currentHighlights = [];
     }
+    applyHighlightsToContent();
+  }
 }
 
 async function saveHighlights() {
@@ -4456,6 +4598,7 @@ async function saveHighlights() {
     const body = JSON.stringify({ct: ciphertext, iv});
     const url = `/books/${currentBookId}/highlights/`;
     _lastHighlightBeacon = {url, body};
+    _saveAnnotationsCache(currentBookId, 'highlights', ciphertext, iv); // keep local cache current
     await fetch(url, {
       method: 'POST',
       headers: {'Content-Type': 'application/json', 'X-CSRFToken': getCsrfToken()},