Fix matching: add missing subtitle field, proper error logging, match-all endpoint

- MatchResult was missing subtitle field, causing AttributeError in
  _apply_match that silently killed every background match task
- Wrap _apply_match in try/except with exc_info logging so failures
  are visible in docker compose logs backend
- New POST /api/libraries/:id/match-all endpoint to trigger matching
  for all unlocked items (useful for items scanned before the fix)
- Admin UI: Match button per library next to the Scan button

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

backend/app/routers/libraries.py

@@ -219,3 +219,33 @@ async def scan_library(
     background_tasks.add_task(scan_library_task, library_id, job.id)
 
     return {"id": job.id, "type": "scan", "libraryId": library_id}
+
+
+@router.post("/{library_id}/match-all")
+async def match_all_items(
+    library_id: str,
+    background_tasks: BackgroundTasks,
+    admin: User = Depends(require_admin),
+    db: AsyncSession = Depends(get_db),
+):
+    """Startet Matching für alle nicht-gematchten Items der Library."""
+    result = await db.execute(select(Library).where(Library.id == library_id))
+    if not result.scalar_one_or_none():
+        raise HTTPException(status_code=404, detail="Library not found")
+
+    items_result = await db.execute(
+        select(LibraryItem).where(
+            LibraryItem.library_id == library_id,
+            LibraryItem.match_locked == False,
+        )
+    )
+    items = items_result.scalars().all()
+    item_ids = [i.id for i in items]
+
+    async def _run_all():
+        from ..services.matcher import match_audiobook
+        for iid in item_ids:
+            await match_audiobook(iid)
+
+    background_tasks.add_task(_run_all)
+    return {"queued": len(item_ids), "libraryId": library_id}

backend/app/services/matcher.py

@@ -233,12 +233,15 @@ async def match_audiobook(item_id: str):
                 logger.warning(f"{source_name} Fehler: {e}")
 
         if best and best_score >= UNCERTAIN_THRESHOLD:
-            await _apply_match(db, item, best, best_score)
-            logger.info(f"Match angewendet: '{item.title}' ← {best.source} ({best_score:.2f})")
+            try:
+                await _apply_match(db, item, best, best_score)
+                await db.commit()
+                logger.info(f"Match angewendet: '{item.title}' ← {best.source} ({best_score:.2f})")
+            except Exception as e:
+                logger.error(f"_apply_match fehlgeschlagen für '{title}': {e}", exc_info=True)
         else:
             logger.info(f"Kein Match für '{title}' (beste Konfidenz: {best_score:.2f})")
-
-        await db.commit()
+            await db.commit()
 
 
 async def search_for_item(title: str, author: str | None = None) -> list[dict]:

backend/app/services/matching/base.py

@@ -7,6 +7,7 @@ class MatchResult:
     source: str  # musicbrainz / open_library / google_books
     source_id: str
     title: str
+    subtitle: str | None = None
     author: str | None = None
     narrator: str | None = None
     description: str | None = None