fix: ensure SSR always fetches fresh assets from database

Root cause: Dockerfile copied only browser/ to nginx; server/server.mjs
was built but never deployed or executed. Prerender baked DEFAULT_CONFIG
into static HTML with no API at build time, causing stale content on
every initial paint.

Changes:
- Dockerfile: serve stage uses node:22-alpine, installs nginx via apk,
  copies both browser/ and server/ bundles from build stage
- docker-entrypoint.sh: starts Angular SSR Node process on port 4200,
  waits for readiness, exports SSR_API_BASE_URL, then exec nginx
- nginx.conf.template: adds upstream ssr_backend block (127.0.0.1:4200),
  proxies / to SSR backend, static assets served directly with 1y cache
- app.server.routes.ts: all routes switched from RenderMode.Prerender
  to RenderMode.Server for zero stale content
- server.ts: removed dead prerender code (PRERENDERED_ROUTES,
  isPrerenderedRoute, allowStaticRouteRender)
- main.server.ts: injects SSR-aware apiBaseUrl via APP_CONFIG
  (reads SSR_API_BASE_URL env var)
- server.spec.ts: updated 5 test suites + added 5 new suites (31 tests)
  covering server.ts cleanup, RenderMode.Server, entrypoint lifecycle,
  Dockerfile build, nginx upstream proxy, and API URL injection
- vitest.config.ts: added server.spec.ts to include pattern

Request flow: Browser -> nginx (port 80) -> SSR server (port 4200)
-> Angular SSR -> HttpClient -> localhost:80/api/station-config
-> nginx proxies to api:8000 -> fresh data rendered in HTML

vitest.config.ts

@@ -3,7 +3,7 @@ export default {
   test: {
     globals: true,
     environment: 'jsdom',
-    include: ['src/**/*.spec.ts'],
+    include: ['src/**/*.spec.ts', 'server.spec.ts'],
     setupFiles: ['src/test-setup.ts'],
     reporters: ['default'],
     coverage: {