Add first-run setup wizard and file browser for library creation

- On first start (no users in DB), show a setup page in the web UI
  to create the admin account instead of reading credentials from .env
- New public endpoints: GET /api/setup/status, POST /api/setup
- New admin endpoint: GET /api/filebrowser?path=... for directory listing
- FileBrowser modal component with navigation, used in Admin > Libraries
- Remove _seed_admin / _seed_default_library from server startup

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

backend/app/main.py

@@ -1,4 +1,3 @@
-import uuid
 import logging
 import os
 from contextlib import asynccontextmanager
@@ -7,13 +6,10 @@ from fastapi.middleware.cors import CORSMiddleware
 from fastapi.staticfiles import StaticFiles
 from apscheduler.schedulers.asyncio import AsyncIOScheduler
 
-from .database import init_db, AsyncSessionLocal
+from .database import init_db
 from .config import get_settings
-from .models import User, Library
-from .services.auth import hash_password, verify_password, create_token
 from .services.file_watcher import start_file_watcher, stop_file_watcher
 from .services.podcast_feed import update_all_feeds
-from sqlalchemy import select
 
 logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(name)s: %(message)s")
 logger = logging.getLogger(__name__)
@@ -21,50 +17,6 @@ logger = logging.getLogger(__name__)
 _scheduler = AsyncIOScheduler()
 
 
-async def _seed_admin():
-    settings = get_settings()
-    async with AsyncSessionLocal() as db:
-        result = await db.execute(select(User).where(User.is_admin == True))
-        existing = result.scalar_one_or_none()
-        if existing:
-            if not verify_password(settings.admin_password, existing.password_hash):
-                existing.password_hash = hash_password(settings.admin_password)
-                await db.commit()
-                logger.info("Admin-Passwort aus ENV aktualisiert.")
-            return
-        logger.info(f"Lege Admin-User an: {settings.admin_username}")
-        admin = User(
-            id=str(uuid.uuid4()),
-            username=settings.admin_username,
-            email=settings.admin_email,
-            password_hash=hash_password(settings.admin_password),
-            is_admin=True,
-        )
-        db.add(admin)
-        await db.flush()
-        admin.token = create_token(admin.id)
-        await db.commit()
-        logger.info("Admin-User angelegt.")
-
-
-async def _seed_default_library():
-    settings = get_settings()
-    async with AsyncSessionLocal() as db:
-        result = await db.execute(select(Library))
-        if result.scalar_one_or_none():
-            return
-        folder_id = str(uuid.uuid4())
-        lib = Library(
-            id=str(uuid.uuid4()),
-            name="Hörbücher",
-            display_name="Hörbücher",
-            folders=[{"id": folder_id, "fullPath": settings.audiofiles_path}],
-            media_type="book",
-            settings={"icon": "headphones", "provider": "google"},
-        )
-        db.add(lib)
-        await db.commit()
-        logger.info(f"Standard-Library angelegt: {settings.audiofiles_path}")
 
 
 @asynccontextmanager
@@ -74,8 +26,6 @@ async def lifespan(app: FastAPI):
         os.makedirs(d, exist_ok=True)
 
     await init_db()
-    await _seed_admin()
-    await _seed_default_library()
     await start_file_watcher()
 
     # Podcast-Feed-Scheduler
@@ -105,8 +55,9 @@ 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
+from .routers import matching, podcasts, setup, filebrowser
 
+app.include_router(setup.router)
 app.include_router(auth.router)
 app.include_router(libraries.router)
 app.include_router(items.router)
@@ -116,3 +67,4 @@ app.include_router(users.router)
 app.include_router(settings_router.router)
 app.include_router(matching.router)
 app.include_router(podcasts.router)
+app.include_router(filebrowser.router)