feat: add videodb media index with Docker stack

- Add videodb PHP/MySQL media collection manager (Blu-ray, DVD, CD)
- Dockerfile: PHP 8.1 + Apache with GD/mysqli/exif extensions
- docker-compose.yml: app on port 6761 + MySQL 8.0 with health checks
- docker-entrypoint.sh: auto-generates config.inc.php from env vars,
  waits for MySQL, initializes DB schema idempotently
- init-db.php: CLI schema installer using app's own prefix_query() logic
- Persistent volumes for DB, cache, and cover images

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

docker-compose.yml

@@ -0,0 +1,47 @@
+services:
+
+  app:
+    build:
+      context: ./videodb
+    container_name: videodb_app
+    ports:
+      - "6761:80"
+    environment:
+      DB_HOST: db
+      DB_USER: videodb
+      DB_PASSWORD: videodb_secret
+      DB_NAME: videodb
+      DB_PREFIX: videodb_
+    depends_on:
+      db:
+        condition: service_healthy
+    volumes:
+      # Persist cover images and cached thumbnails across rebuilds
+      - videodb_cache:/var/www/html/cache
+      - videodb_images:/var/www/html/images
+    restart: unless-stopped
+
+  db:
+    image: mysql:8.0
+    container_name: videodb_db
+    environment:
+      MYSQL_ROOT_PASSWORD: root_secret
+      MYSQL_DATABASE: videodb
+      MYSQL_USER: videodb
+      MYSQL_PASSWORD: videodb_secret
+    volumes:
+      - videodb_db:/var/lib/mysql
+    # MySQL 8 defaults to caching_sha2_password; keep native auth for broad client compat
+    command: --default-authentication-plugin=mysql_native_password
+    healthcheck:
+      test: ["CMD", "mysqladmin", "ping", "-h", "localhost", "-u", "videodb", "-pvideodb_secret"]
+      interval: 10s
+      timeout: 5s
+      retries: 12
+      start_period: 30s
+    restart: unless-stopped
+
+volumes:
+  videodb_db:
+  videodb_cache:
+  videodb_images: