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>

angular.json

@@ -29,12 +29,6 @@
 						"styles": [
 							"src/styles.scss"
 						],
-						"server": "src/main.server.ts",
-						"outputMode": "server",
-						"ssr": {
-							"entry": "src/server.ts"
-						},
-						"prerender": false,
 						"allowedCommonJsDependencies": [
 							"deepmerge",
 							"moment-timezone",