Add global mini-player and improve configuration

- Add global activeRoom store for persistent WebSocket connection
- Add MiniPlayer component for playback controls across pages
- Add chunked S3 streaming with 64KB chunks and Range support
- Add queue item removal button
- Move DB credentials to environment variables
- Update .env.example with DB configuration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

docker-compose.yml

@@ -4,15 +4,15 @@ services:
   db:
     image: postgres:15-alpine
     environment:
-      POSTGRES_USER: postgres
-      POSTGRES_PASSWORD: postgres
-      POSTGRES_DB: enigfm
+      POSTGRES_USER: ${DB_USER}
+      POSTGRES_PASSWORD: ${DB_PASSWORD}
+      POSTGRES_DB: ${DB_NAME}
     volumes:
       - postgres_data:/var/lib/postgresql/data
     ports:
       - "4002:5432"
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      test: ["CMD-SHELL", "pg_isready -U ${DB_USER}"]
       interval: 5s
       timeout: 5s
       retries: 5
@@ -22,7 +22,7 @@ services:
       context: ./backend
       dockerfile: Dockerfile
     environment:
-      DATABASE_URL: postgresql://postgres:postgres@db:5432/enigfm
+      DATABASE_URL: postgresql://${DB_USER}:${DB_PASSWORD}@db:5432/${DB_NAME}
       SECRET_KEY: ${SECRET_KEY:-change-me-in-production}
       S3_ENDPOINT_URL: ${S3_ENDPOINT_URL}
       S3_ACCESS_KEY: ${S3_ACCESS_KEY}