feat: integrate React frontend with Go backend and containerize with Docker

- Rewrite Dockerfile with 4-stage build process:
  - Stage 1: Build React SPA with Bun (oven/bun:latest)
  - Stage 2: Build Go binary with embedded frontend (golang:1.25-alpine)
  - Stage 3: Fetch runtime dependencies (alpine:3.23)
  - Stage 4: Minimal runtime container (busybox:1.37.0-musl)
- Add comprehensive comments explaining each build stage
- Add build verification checks to ensure frontend embeds correctly
- Update compose.yaml with environment variables (FB_PORT=80, FB_ADDRESS=0.0.0.0)
- Add docker-compose.dev.yaml for development with hot reload support
- Modify http/static.go to serve 'index.html' instead of 'public/index.html'
- Final production image: ~50MB with non-root user and health checks
- Enable both production and development Docker workflows

docker-compose.dev.yaml

@@ -0,0 +1,72 @@
+# Development environment - runs Go backend and serves frontend from Vite dev server
+# 
+# This is useful for development as it:
+# 1. Runs the Go backend in a container for isolated environment
+# 2. Allows running React dev server locally with HMR
+#
+# Setup:
+#   1. Start containers: docker compose -f docker-compose.dev.yaml up
+#   2. In another terminal, run frontend dev server: cd frontend && bun run dev
+#   3. Access the app at: http://localhost:5173 (frontend dev server)
+#   4. API calls proxy to http://backend:8080
+#
+# For production build, use: docker compose up --build
+
+services:
+  backend:
+    container_name: filebrowser_backend
+    build:
+      dockerfile: Dockerfile.dev
+      context: .
+    restart: unless-stopped
+    networks:
+      - filebrowser
+    ports:
+      - "8080:8080"
+    volumes:
+      - ./:/app
+      - /app/frontend/node_modules
+    environment:
+      - FB_PORT=8080
+      - FB_ADDRESS=0.0.0.0
+      - REDIS_CACHE_URL=redis://default:filebrowser@redis:6379
+    depends_on:
+      redis:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD", "wget", "--quiet", "--tries=1", "--spider", "http://localhost:8080/health"]
+      interval: 10s
+      timeout: 5s
+      retries: 3
+      start_period: 10s
+
+  redis:
+    container_name: filebrowser_redis_dev
+    image: redis:7-alpine
+    restart: unless-stopped
+    networks:
+      - filebrowser
+    command:
+      - sh
+      - -c
+      - |
+        cat > /tmp/users.acl <<'EOF'
+        user default on >filebrowser ~* +@all
+        EOF
+        redis-server --aclfile /tmp/users.acl
+    volumes:
+      - redis_data_dev:/data
+    healthcheck:
+      test: ["CMD", "redis-cli", "ping"]
+      interval: 5s
+      timeout: 3s
+      retries: 5
+      start_period: 5s
+
+networks:
+  filebrowser:
+    driver: bridge
+
+volumes:
+  redis_data_dev:
+    driver: local