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)