feat: graceful shutdown and frontend build in Docker

- Add SIGTERM/Ctrl+C signal handling with graceful connection draining
- Close database pool cleanly on shutdown
- Add frontend-builder stage to Dockerfile (node:22-alpine, npm ci + build)
- Move Docker build context to project root so both frontend/ and backend/ are accessible
- Frontend dist/ copied into container at ./static/ for the backend to serve

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/Dockerfile

@@ -1,12 +1,29 @@
 # ===================================================================
-# Stage 1: Build the Rust backend
+# Stage 1: Build the frontend
+# ===================================================================
+FROM node:22-alpine AS frontend-builder
+
+WORKDIR /app
+
+# Copy package files first for dependency caching
+COPY frontend/package.json frontend/package-lock.json ./
+
+RUN npm ci
+
+# Copy source and build
+COPY frontend/ ./
+
+RUN npm run build
+
+# ===================================================================
+# Stage 2: Build the Rust backend
 # ===================================================================
 FROM rust:1.85-bookworm AS builder
 
 WORKDIR /app
 
 # Copy manifests first for dependency caching
-COPY Cargo.toml Cargo.lock ./
+COPY backend/Cargo.toml backend/Cargo.lock ./
 
 # Create a dummy main.rs to build dependencies
 RUN mkdir src && echo "fn main() {}" > src/main.rs
@@ -14,8 +31,8 @@ RUN cargo build --release
 RUN rm -rf src
 
 # Copy the actual source code and migrations
-COPY src/ src/
-COPY migrations/ migrations/
+COPY backend/src/ src/
+COPY backend/migrations/ migrations/
 
 # Set sqlx offline mode (no live DB needed during build)
 ENV SQLX_OFFLINE=true
@@ -26,7 +43,7 @@ RUN touch src/main.rs
 RUN cargo build --release
 
 # ===================================================================
-# Stage 2: Minimal runtime image
+# Stage 3: Minimal runtime image
 # ===================================================================
 FROM debian:bookworm-slim AS runtime
 
@@ -50,6 +67,9 @@ COPY --from=builder /app/target/release/ai-synth-backend ./ai-synth-backend
 # Copy migrations (run at startup)
 COPY --from=builder /app/migrations/ ./migrations/
 
+# Copy built frontend
+COPY --from=frontend-builder /app/dist/ ./static/
+
 # Set ownership
 RUN chown -R appuser:appuser /app
 

backend/src/main.rs

@@ -59,6 +59,7 @@ async fn main() -> anyhow::Result<()> {
                 tracing::warn!("Failed to load provider rate limits from DB: {:?}. Using defaults.", e);
             }
 
+            let shutdown_pool = state.pool.clone();
             let app = router::build_router(state, &config);
 
             let addr = format!("0.0.0.0:{}", config.port);
@@ -69,8 +70,13 @@ async fn main() -> anyhow::Result<()> {
                 .context("Failed to bind to address")?;
 
             axum::serve(listener, app)
+                .with_graceful_shutdown(shutdown_signal())
                 .await
                 .context("Server error")?;
+
+            tracing::info!("Server shut down, closing database pool...");
+            shutdown_pool.close().await;
+            tracing::info!("Shutdown complete.");
         }
         Commands::CreateAdmin { email } => {
             tracing::info!("Creating admin user: {}", email);
@@ -103,3 +109,28 @@ async fn run_migrations(pool: &sqlx::PgPool) -> anyhow::Result<()> {
     tracing::info!("Migrations complete.");
     Ok(())
 }
+
+/// Wait for SIGTERM or Ctrl+C, then return to trigger graceful shutdown.
+async fn shutdown_signal() {
+    let ctrl_c = async {
+        tokio::signal::ctrl_c()
+            .await
+            .expect("failed to install Ctrl+C handler");
+    };
+
+    #[cfg(unix)]
+    let terminate = async {
+        tokio::signal::unix::signal(tokio::signal::unix::SignalKind::terminate())
+            .expect("failed to install SIGTERM handler")
+            .recv()
+            .await;
+    };
+
+    #[cfg(not(unix))]
+    let terminate = std::future::pending::<()>();
+
+    tokio::select! {
+        _ = ctrl_c => tracing::info!("Received Ctrl+C, starting graceful shutdown..."),
+        _ = terminate => tracing::info!("Received SIGTERM, starting graceful shutdown..."),
+    }
+}

docker-compose.yml

@@ -1,8 +1,8 @@
 services:
   app:
     build:
-      context: ./backend
-      dockerfile: Dockerfile
+      context: .
+      dockerfile: backend/Dockerfile
     container_name: ai-synth
     restart: unless-stopped
     env_file: .env