Add logging system: app.log + matching.log with admin viewer

- Backend: RotatingFileHandler for app.log (all) and matching.log (matcher/matching services)
- New GET/DELETE /api/logs/{app|matching} endpoints (admin-only)
- matcher.py: improved cover-download logging (URL, bytes, HTTP errors, missing cover URL)
- Frontend: Logs tab in Admin panel with log switcher, line count selector, color-coded ERROR/WARNING lines, clear button

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

backend/app/main.py

@@ -1,4 +1,5 @@
 import logging
+import logging.handlers
 import os
 from contextlib import asynccontextmanager
 from fastapi import FastAPI
@@ -11,14 +12,45 @@ from .config import get_settings
 from .services.file_watcher import start_file_watcher, stop_file_watcher
 from .services.podcast_feed import update_all_feeds
 
-logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(name)s: %(message)s")
+
+def _setup_logging():
+    settings = get_settings()
+    os.makedirs(settings.log_dir, exist_ok=True)
+
+    fmt = logging.Formatter("%(asctime)s %(levelname)s %(name)s: %(message)s")
+
+    root = logging.getLogger()
+    root.setLevel(logging.INFO)
+
+    # Console (bestehend)
+    console = logging.StreamHandler()
+    console.setFormatter(fmt)
+    root.addHandler(console)
+
+    # app.log — alle Logs
+    app_fh = logging.handlers.RotatingFileHandler(
+        os.path.join(settings.log_dir, "app.log"),
+        maxBytes=5_000_000, backupCount=2, encoding="utf-8"
+    )
+    app_fh.setFormatter(fmt)
+    root.addHandler(app_fh)
+
+    # matching.log — nur Matching-bezogene Logger
+    match_fh = logging.handlers.RotatingFileHandler(
+        os.path.join(settings.log_dir, "matching.log"),
+        maxBytes=5_000_000, backupCount=2, encoding="utf-8"
+    )
+    match_fh.setFormatter(fmt)
+    for name in ("app.services.matcher", "app.services.matching"):
+        logging.getLogger(name).addHandler(match_fh)
+
+
+_setup_logging()
 logger = logging.getLogger(__name__)
 
 _scheduler = AsyncIOScheduler()
 
 
-
-
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     settings = get_settings()
@@ -28,7 +60,6 @@ async def lifespan(app: FastAPI):
     await init_db()
     await start_file_watcher()
 
-    # Podcast-Feed-Scheduler
     _scheduler.add_job(update_all_feeds, "interval", hours=settings.podcast_update_interval_hours, id="feed_update")
     _scheduler.start()
 
@@ -55,7 +86,7 @@ if os.path.exists(settings.covers_dir):
     app.mount("/covers", StaticFiles(directory=settings.covers_dir), name="covers")
 
 from .routers import auth, libraries, items, stream, me, users, settings as settings_router
-from .routers import matching, podcasts, setup, filebrowser
+from .routers import matching, podcasts, setup, filebrowser, logs
 
 app.include_router(setup.router)
 app.include_router(auth.router)
@@ -68,3 +99,4 @@ app.include_router(settings_router.router)
 app.include_router(matching.router)
 app.include_router(podcasts.router)
 app.include_router(filebrowser.router)
+app.include_router(logs.router)

backend/app/routers/logs.py

@@ -0,0 +1,57 @@
+import os
+from fastapi import APIRouter, Depends, HTTPException, Query
+from ..dependencies import require_admin
+from ..models.user import User
+from ..config import get_settings
+
+router = APIRouter(prefix="/api/logs", tags=["logs"])
+
+_LOG_FILES = {
+    "app": "app.log",
+    "matching": "matching.log",
+}
+
+
+@router.get("/{log_name}")
+async def get_log(
+    log_name: str,
+    lines: int = Query(300, ge=10, le=5000),
+    _admin: User = Depends(require_admin),
+):
+    if log_name not in _LOG_FILES:
+        raise HTTPException(status_code=404, detail="Unbekannte Log-Datei")
+
+    settings = get_settings()
+    path = os.path.join(settings.log_dir, _LOG_FILES[log_name])
+
+    if not os.path.exists(path):
+        return {"lines": [], "total": 0, "showing": 0, "exists": False, "path": path}
+
+    with open(path, "r", encoding="utf-8", errors="replace") as f:
+        all_lines = f.readlines()
+
+    last = all_lines[-lines:]
+    return {
+        "lines": [l.rstrip("\n") for l in last],
+        "total": len(all_lines),
+        "showing": len(last),
+        "exists": True,
+        "path": path,
+    }
+
+
+@router.delete("/{log_name}")
+async def clear_log(
+    log_name: str,
+    _admin: User = Depends(require_admin),
+):
+    if log_name not in _LOG_FILES:
+        raise HTTPException(status_code=404, detail="Unbekannte Log-Datei")
+
+    settings = get_settings()
+    path = os.path.join(settings.log_dir, _LOG_FILES[log_name])
+
+    if os.path.exists(path):
+        open(path, "w").close()
+
+    return {"success": True}

backend/app/services/matcher.py

@@ -85,6 +85,7 @@ async def _download_cover(url: str, item_id: str) -> str | None:
     if ".png" in url:
         ext = ".png"
     dest = os.path.join(settings.covers_dir, f"{item_id}{ext}")
+    logger.info(f"Cover-Download: {url}")
     try:
         async with httpx.AsyncClient(timeout=20, follow_redirects=True) as client:
             r = await client.get(url)
@@ -92,9 +93,12 @@ async def _download_cover(url: str, item_id: str) -> str | None:
                 os.makedirs(settings.covers_dir, exist_ok=True)
                 with open(dest, "wb") as f:
                     f.write(r.content)
+                logger.info(f"Cover gespeichert: {dest} ({len(r.content)} Bytes)")
                 return dest
+            else:
+                logger.warning(f"Cover-Download HTTP {r.status_code}: {url}")
     except Exception as e:
-        logger.warning(f"Cover-Download fehlgeschlagen ({url}): {e}")
+        logger.warning(f"Cover-Download Fehler ({url}): {e}")
     return None
 
 
@@ -133,6 +137,8 @@ async def _apply_match(db: AsyncSession, item: LibraryItem, result: MatchResult,
         cover_path = await _download_cover(result.cover_url, item.id)
         if cover_path:
             item.cover_path = cover_path
+    elif not result.cover_url:
+        logger.info(f"Kein Cover-URL in Match-Ergebnis ({result.source}: {result.source_id})")
 
     # Kapitel aus MusicBrainz-Tracklisting
     if result.chapters: