feat(spa): proxy /api in dev-server, relative bffApiBaseUrl

Make the SPAs reach the BFF same-origin via the Angular dev-server's
proxy, so the dockerised dev mode (ADR-0030) works when the SPA is
accessed from a remote browser (e.g. http://<vm-ip>:4200/) — and CORS
is bypassed in dev altogether.

- New proxy.conf.js per SPA: /api -> ${BFF_TARGET:-http://localhost:3000}
  (JS form so the env var can swap the target at startup without a
  rebuild).
- project.json serve.options.proxyConfig wired in for both apps.
- environment.ts (shell + admin) bffApiBaseUrl: 'http://localhost:3000/api'
  -> '/api'. Production siblings can still set an absolute origin if
  the SPA and BFF live on different hosts; tracing.ts resolves either
  form against window.location.origin.
- tracing.ts: new URL(env, window.location.origin) — relative bases no
  longer throw, absolute bases keep their own origin.
- dev.compose.yml: BFF_TARGET=http://portal-bff:3000 on portal-shell
  and portal-admin so the proxy hits the BFF container by Compose DNS.
  Native nx serve leaves it unset and falls back to localhost.

OTel exporter URL and cross-SPA links remain absolute — same remote-
browser issue, but not blocking the 'Backend unreachable' path this
PR targets. Out of scope here, follow-up if needed.

Stacked on top of feat/dockerised-dev-mode.

apps/portal-shell/project.json

@@ -83,6 +83,9 @@
     "serve": {
       "continuous": true,
       "executor": "@angular/build:dev-server",
+      "options": {
+        "proxyConfig": "apps/portal-shell/proxy.conf.js"
+      },
       "configurations": {
         "production": {
           "buildTarget": "portal-shell:build:production"

apps/portal-shell/proxy.conf.js

@@ -0,0 +1,32 @@
+// Angular dev-server proxy for portal-shell.
+//
+// Lets the SPA call `/api/...` as a SAME-ORIGIN request — the dev
+// server intercepts it and proxies to the BFF. Two wins:
+//   - the browser no longer pins the BFF to `localhost:3000`, so the
+//     SPA works when accessed from a different host (e.g. `http://
+//     <vm-ip>:4200/` in the ADR-0030 dockerised dev mode, where the
+//     browser may not be on the same machine as the BFF);
+//   - CORS is bypassed entirely in dev (same origin), so the BFF's
+//     `CORS_ALLOWED_ORIGINS` allowlist no longer has to enumerate the
+//     workstation/VM hostnames a developer might use.
+//
+// Target resolution:
+//   - native `nx serve`        → defaults to http://localhost:3000
+//                                (the BFF on the same machine).
+//   - Compose `apps` profile   → BFF_TARGET=http://portal-bff:3000 is
+//                                set in dev.compose.yml so the proxy
+//                                hits the BFF container by name.
+//
+// JS form (not JSON) is deliberate: it is the only Angular-supported
+// proxy-config form that can read `process.env` at dev-server startup,
+// which is what makes the Docker / native swap work without rebuilds.
+
+const target = process.env['BFF_TARGET'] ?? 'http://localhost:3000';
+
+module.exports = {
+  '/api': {
+    target,
+    secure: false,
+    changeOrigin: true,
+  },
+};

apps/portal-shell/src/environments/environment.ts

@@ -18,12 +18,24 @@
  */
 export const environment = {
   /**
-   * Origin + prefix of the BFF HTTP API. The SPA prepends this to
-   * every backend call (`${bffApiBaseUrl}/health`, etc.) and derives
-   * the OTel trace-header propagation pattern from its origin (see
-   * `observability/tracing.ts`).
+   * Prefix of the BFF HTTP API. The SPA prepends this to every
+   * backend call (`${bffApiBaseUrl}/health`, etc.) and derives the
+   * OTel trace-header propagation pattern from its resolved origin
+   * (see `observability/tracing.ts`).
+   *
+   * Relative path: the Angular dev-server proxies `/api/*` to the
+   * BFF (see `proxy.conf.js`, BFF target overridable via the
+   * `BFF_TARGET` env var — set by the ADR-0030 `apps` Compose
+   * profile to `http://portal-bff:3000`). This keeps every BFF call
+   * same-origin in the browser, so the SPA works whether it is
+   * accessed via `localhost:4200`, the VM IP, or any other host —
+   * and the BFF's `CORS_ALLOWED_ORIGINS` no longer has to enumerate
+   * every developer-side hostname. Production siblings
+   * (`environment.prod.ts`, etc.) may set an absolute origin when
+   * the SPA and BFF live on different hosts; `tracing.ts` resolves
+   * either form against `window.location.origin`.
    */
-  bffApiBaseUrl: 'http://localhost:3000/api',
+  bffApiBaseUrl: '/api',
 
   /**
    * Name of the BFF's CSRF cookie. Mirrors the BFF's

apps/portal-shell/src/observability/tracing.ts

@@ -55,7 +55,13 @@ const SERVICE_VERSION = 'dev';
 // so a deploy-time change to `bffApiBaseUrl` automatically propagates
 // `traceparent` to the right origin. RegExp special chars are escaped
 // before going into the source.
-const bffOrigin = new URL(environment.bffApiBaseUrl).origin;
+//
+// Resolved against `window.location.origin` so a relative
+// `bffApiBaseUrl` (e.g. `/api` for the dev-server proxy in
+// `proxy.conf.js`) yields the current origin; an absolute
+// `bffApiBaseUrl` (e.g. cross-origin production) keeps its own origin
+// (the second `URL` arg is ignored when the first is absolute).
+const bffOrigin = new URL(environment.bffApiBaseUrl, window.location.origin).origin;
 const bffOriginRegex = new RegExp(`^${bffOrigin.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')}/.*`);
 
 const provider = new WebTracerProvider({