feat(server): serve the client-only build with Bun

Angular's server build needs Node loader hooks that Bun does not apply,
and every route is client-rendered, so Angular now builds a client-only
bundle and a small Bun.serve server delivers it: hashed assets with the
one-year cache, index.html revalidated, extension-less routes falling
back to index.html, missing assets 404, traversal and malformed paths
rejected, and other methods 405. Express, @angular/ssr and the unused
hydration provider are removed. Both Docker stages use the pinned
oven/bun:1.4.3-alpine image without Node, and the health checks use
Bun's fetch.

Refs #292

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Dockerfile

@@ -1,48 +1,30 @@
-# Stage 1: Build the Angular application
-FROM oven/bun:alpine AS builder
+# Stage 1: Build the Angular application and the Bun static server
+FROM oven/bun:1.4.3-alpine@sha256:629e17411f1f129dbec3af78d5af9c9f2a937435c80349437206c6b0b7422373 AS builder
 
-# Install nodejs to support Angular prerendering worker threads
-RUN apk add --no-cache nodejs
-
-# Set working directory
 WORKDIR /app
 
-# Copy package files
-COPY package.json bun.lock* ./
+COPY package.json bun.lock ./
+RUN bun install --frozen-lockfile
 
-# Install dependencies
-RUN bun install
-
-# Copy source code
 COPY . .
 
-# Build the application for production
-RUN bun run build
+# --bun makes Angular's Node-shebang CLI run on Bun instead of a Node on PATH
+RUN bun --bun run build
 
 # Stage 2: Production image
-FROM oven/bun:alpine AS production
+FROM oven/bun:1.4.3-alpine@sha256:629e17411f1f129dbec3af78d5af9c9f2a937435c80349437206c6b0b7422373 AS production
 
-# Set working directory
 WORKDIR /app
 
-# Copy package files
-COPY package.json bun.lock* ./
-
-# Install only production dependencies
-RUN bun install --production
-
-# Copy built application from builder stage
+# The server is a self-contained Bun bundle that serves the browser build, so
+# the runtime has no dependencies to install.
 COPY --from=builder /app/dist ./dist
 
-# Set environment to production
 ENV NODE_ENV=production
 
-# Expose port (default Express port)
 EXPOSE 4000
 
-# Health check
 HEALTHCHECK --interval=30s --timeout=10s --start-period=40s --retries=3 \
-  CMD bun -e "require('http').get('http://localhost:4000', (r) => {process.exit(r.statusCode === 200 ? 0 : 1)})"
+  CMD bun -e "fetch('http://localhost:' + (process.env.PORT || 4000) + '/').then(r => process.exit(r.ok ? 0 : 1), () => process.exit(1))"
 
-# Start the application
-CMD ["bun", "run", "dist/vac-optimizer/server/server.mjs"]
+CMD ["bun", "dist/vac-optimizer/server/server.js"]