chore: beta release v0.5.0-beta

- Bump version to 0.5.0-beta
- Add Apache-2.0 LICENSE (official text) + NOTICE
- Add Docker support: multi-stage Dockerfile + docker-compose
  * non-root user, tini PID 1, gunicorn + uvicorn workers
  * healthcheck, OCI labels, persistent /data volume
- Add GitHub Actions CI (lint/import-check + Docker smoke-test)
- Backend polish:
  * modern lifespan handler (replaces deprecated on_event)
  * explicit sort validation (400 instead of 500)
  * title min_length=1 schema validation
  * configurable data dir + http timeout via env
  * avg_rating helper extracted (DRY)
- Frontend polish:
  * beta badge in title, footer with live version
  * loading spinner on initial fetch
  * updated README, badges, config table, roadmap

app/external.py

@@ -1,7 +1,9 @@
 """Externe Cover-/Metadaten-Quellen (Open Library)."""
+# SPDX-License-Identifier: Apache-2.0
 from __future__ import annotations
 
 import logging
+import os
 from typing import Optional
 
 import httpx
@@ -10,9 +12,10 @@ log = logging.getLogger(__name__)
 
 OL_SEARCH = "https://openlibrary.org/search.json"
 OL_COVER = "https://covers.openlibrary.org/b/isbn/{isbn}-L.jpg"
+DEFAULT_TIMEOUT = float(os.environ.get("WATCHSTACK_HTTP_TIMEOUT", "8"))
 
 
-def lookup_book_by_isbn(isbn: str, *, timeout: float = 8.0) -> Optional[dict]:
+def lookup_book_by_isbn(isbn: str, *, timeout: float = DEFAULT_TIMEOUT) -> Optional[dict]:
     """Sucht Buchdaten anhand ISBN via Open Library."""
     if not isbn:
         return None
@@ -41,7 +44,7 @@ def lookup_book_by_isbn(isbn: str, *, timeout: float = 8.0) -> Optional[dict]:
     }
 
 
-def lookup_book_by_title(title: str, *, timeout: float = 8.0) -> Optional[dict]:
+def lookup_book_by_title(title: str, *, timeout: float = DEFAULT_TIMEOUT) -> Optional[dict]:
     """Sucht Buchdaten anhand Titel (Fallback)."""
     if not title:
         return None