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

Dockerfile

@@ -1,4 +1,63 @@
-## Multistage build: First stage fetches dependencies
+# ============================================================================
+# STAGE 1: Build Frontend (React 18 + Bun)
+# ============================================================================
+# This stage builds the React SPA with TypeScript, Tailwind CSS, and Vite
+# Output: frontend/dist/ with optimized static assets
+# ============================================================================
+FROM oven/bun:latest AS frontend-builder
+
+WORKDIR /app/frontend
+
+# Copy frontend source
+COPY frontend/ .
+
+# Install dependencies and build frontend
+# - bun install: Fast package installation
+# - bun run build: TypeScript type check + Vite optimization
+RUN bun install && \
+    bun run build
+
+# Verify build output exists
+RUN test -f dist/index.html || (echo "Frontend build failed!" && exit 1)
+
+# ============================================================================
+# STAGE 2: Build Backend (Go 1.25) with embedded frontend
+# ============================================================================
+# This stage builds the Go server with the React SPA embedded
+# Uses Go's embed package to include all static assets
+# Output: filebrowser binary (statically linked, no dependencies)
+# ============================================================================
+FROM golang:1.25-alpine AS backend-builder
+
+WORKDIR /app
+
+# Install build dependencies
+RUN apk add --no-cache git ca-certificates
+
+# Copy the entire project
+COPY . .
+
+# Copy built frontend from stage 1 into the frontend Go package
+# The frontend/frontend.go file uses //go:embed dist to include these files
+COPY --from=frontend-builder /app/frontend/dist ./frontend/dist
+
+# Download Go dependencies
+RUN go mod download
+
+# Build the Go binary with embedded frontend
+# - CGO_ENABLED=0: Static linking (no libc dependency)
+# - GOOS=linux: Linux target
+# - GOARCH=amd64: 64-bit x86 architecture
+# - The frontend/dist directory is embedded via the //go:embed directive
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -o filebrowser .
+
+# Verify binary was created and contains embedded assets
+RUN test -f filebrowser || (echo "Go build failed!" && exit 1) && \
+    strings filebrowser | grep -q "index.html" || (echo "Frontend not embedded!" && exit 1)
+
+# ============================================================================
+# STAGE 3: Fetch dependencies and base tools
+# ============================================================================
 FROM alpine:3.23 AS fetcher
 
 # install and copy ca-certificates, mailcap, and tini-static; download JSON.sh
@@ -6,21 +65,31 @@ RUN apk update && \
     apk --no-cache add ca-certificates mailcap tini-static && \
     wget -O /JSON.sh https://raw.githubusercontent.com/dominictarr/JSON.sh/0d5e5c77365f63809bf6e77ef44a1f34b0e05840/JSON.sh
 
-## Second stage: Use lightweight BusyBox image for final runtime environment
+# ============================================================================
+# STAGE 4: Final Runtime Image (Minimal)
+# ============================================================================
+# Lightweight runtime using busybox (~50MB total image size)
+# Only includes the compiled binary and essential runtime dependencies
+# ============================================================================
 FROM busybox:1.37.0-musl
 
-# Define non-root user UID and GID
+# Define non-root user UID and GID for security
 ENV UID=1000
 ENV GID=1000
 
-# Create user group and user
+# Create unprivileged user and group
 RUN addgroup -g $GID user && \
     adduser -D -u $UID -G user user
 
-# Copy binary, scripts, and configurations into image with proper ownership
-COPY --chown=user:user filebrowser /bin/filebrowser
+# Copy compiled binary from backend builder
+# The binary includes the React SPA (frontend/dist) via Go's embed package
+COPY --chown=user:user --from=backend-builder /app/filebrowser /bin/filebrowser
+
+# Copy initialization and configuration scripts
 COPY --chown=user:user docker/common/ /
 COPY --chown=user:user docker/alpine/ /
+
+# Copy runtime dependencies from fetcher stage
 COPY --chown=user:user --from=fetcher /sbin/tini-static /bin/tini
 COPY --from=fetcher /JSON.sh /JSON.sh
 COPY --from=fetcher /etc/ca-certificates.conf /etc/ca-certificates.conf
@@ -28,19 +97,27 @@ COPY --from=fetcher /etc/ca-certificates /etc/ca-certificates
 COPY --from=fetcher /etc/mime.types /etc/mime.types
 COPY --from=fetcher /etc/ssl /etc/ssl
 
-# Create data directories, set ownership, and ensure healthcheck script is executable
+# Create persistent data directories with proper ownership
 RUN mkdir -p /config /database /srv && \
-    chown -R user:user /config /database /srv \
-    && chmod +x /healthcheck.sh
+    chown -R user:user /config /database /srv && \
+    chmod +x /healthcheck.sh /init.sh
 
-# Define healthcheck script
+# Health check configuration
+# Verifies the frontend is being served correctly
 HEALTHCHECK --start-period=2s --interval=5s --timeout=3s CMD /healthcheck.sh
 
-# Set the user, volumes and exposed ports
+# Run as non-root user
 USER user
 
+# Define persistent volumes
+# /srv: User file storage
+# /config: Configuration files
+# /database: SQLite database
 VOLUME /srv /config /database
 
+# Expose port 80 (internal server runs on 8080, init.sh proxies if needed)
 EXPOSE 80
 
+# Use tini as init process for proper signal handling
+# Then run init.sh which starts the filebrowser binary
 ENTRYPOINT [ "tini", "--", "/init.sh" ]