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

src/app/app.server.routes.ts

@@ -3,16 +3,18 @@ import { RenderMode, ServerRoute } from '@angular/ssr';
 /**
  * Server routes configuration for Angular SSR.
  *
- * The five public routes are prerendered at build time (SSG) for optimal SEO.
- * Authenticated routes (/login, /admin) use SSR for dynamic rendering.
- * All other routes fall back to SSR.
+ * ALL routes use RenderMode.Server — every request hits the SSR server,
+ * which fetches fresh station config from the API before rendering HTML.
+ * This eliminates the stale-asset flash that occurred with prerendered HTML
+ * (prerender runs at build time when the API is unavailable, baking in
+ * DEFAULT_CONFIG values).
  */
 export const serverRoutes: ServerRoute[] = [
-  { path: '', renderMode: RenderMode.Prerender },
-  { path: 'about', renderMode: RenderMode.Prerender },
-  { path: 'schedule', renderMode: RenderMode.Prerender },
-  { path: 'events', renderMode: RenderMode.Prerender },
-  { path: 'contact', renderMode: RenderMode.Prerender },
+  { path: '', renderMode: RenderMode.Server },
+  { path: 'about', renderMode: RenderMode.Server },
+  { path: 'schedule', renderMode: RenderMode.Server },
+  { path: 'events', renderMode: RenderMode.Server },
+  { path: 'contact', renderMode: RenderMode.Server },
   { path: 'login', renderMode: RenderMode.Server },
   { path: 'admin', renderMode: RenderMode.Server },
   { path: '**', renderMode: RenderMode.Server },