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

docker-compose.yml

@@ -0,0 +1,29 @@
+# Komponiert WatchStack mit persistentem Daten-Volume.
+# Optional: Reverse-Proxy (caddy/traefik) davorschalten.
+
+services:
+  watchstack:
+    build: .
+    image: watchstack:beta
+    container_name: watchstack
+    restart: unless-stopped
+    ports:
+      - "${WATCHSTACK_PORT:-8000}:8000"
+    environment:
+      WATCHSTACK_HOST: "0.0.0.0"
+      WATCHSTACK_PORT: "8000"
+      WATCHSTACK_WORKERS: "2"
+      WATCHSTACK_DATA_DIR: "/data"
+      # TZ: "Europe/Berlin"
+    volumes:
+      - watchstack-data:/data
+    healthcheck:
+      test: ["CMD", "python", "-c", "import urllib.request,sys,os; r=urllib.request.urlopen('http://127.0.0.1:8000/api/health',timeout=3); sys.exit(0 if r.status==200 else 1)"]
+      interval: 30s
+      timeout: 5s
+      retries: 3
+      start_period: 10s
+
+volumes:
+  watchstack-data:
+    name: watchstack-data