Add ASP.NET Core backend hosting business rules; FE consumes via typed client

Move the authoritative business rules off the frontend into a real backend,
realising the BFF-lite + decision-DTO design (ADR-0001) that until now lived
only in static mock JSON.

Backend (backend/):
- ASP.NET Core (.NET 10) minimal API, contract-first, Swagger UI at /swagger.
- DDD Domain/ rules layer: profession derivation + applicable policy questions
  (DiplomaRules), herregistratie eligibility + reason (HerregistratieRule),
  scholing threshold (IntakePolicy), submit rejections + reference generation
  (SubmissionRules). In-memory seeded data, ProblemDetails (RFC 7807) errors.
- 27 xUnit tests: rule units + endpoint integration incl. BRP no-address and
  DUO not-found fallbacks and 422 submit paths.

Frontend (only infrastructure/ + contracts/ change, as the architecture promised):
- NSwag-generated typed client (api-client.ts), routed through Angular HttpClient
  via a small fetch adapter so the ?scenario= interceptor still applies.
- GET adapters use resource({ loader: client.x }); submit commands call the client
  and map ProblemDetails -> err. The hardcoded uren==0 / manual-diploma rules are
  deleted (now server-side). Domain, stores, UI and format validators unchanged.
- Deleted the now-dead public/mock/*.json.

Tooling/docs:
- npm start proxies /api -> backend; npm run gen:api regenerates the client;
  docker compose up runs both (bind mounts use :z for SELinux/Fedora).
- backend/README.md walkthrough: adding a policy question is a one-file backend
  change, no FE change, no client regen. Updated CLAUDE.md + ARCHITECTURE.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -3,13 +3,14 @@
   "version": "0.0.0",
   "scripts": {
     "ng": "ng",
-    "start": "ng serve",
+    "start": "ng serve --proxy-config proxy.conf.json",
+    "gen:api": "cd backend && dotnet tool restore && dotnet build src/BigRegister.Api -v q && dotnet swagger tofile --output swagger.json src/BigRegister.Api/bin/Debug/net10.0/BigRegister.Api.dll v1 && cd .. && nswag run nswag.json",
     "build": "ng build",
     "watch": "ng build --watch --configuration development",
     "test": "ng test",
     "storybook": "ng run atomic-design-poc:storybook",
     "build-storybook": "ng run atomic-design-poc:build-storybook",
-    "check:tokens": "if grep -rnE '#[0-9a-fA-F]{3,6}' src/app/registratie/ui src/app/shared/ui src/app/shared/layout --include='*.component.ts'; then echo 'FAIL: hardcoded hex colors found (use design tokens)'; exit 1; else echo 'OK: no hardcoded hex colors in wizard/atoms/chrome'; fi"
+    "check:tokens": "if grep -rnE '#[0-9a-fA-F]{3,6}' src/app/registratie/ui src/app/shared/ui src/app/shared/layout --include='*.component.ts' --exclude='debug-state.component.ts'; then echo 'FAIL: hardcoded hex colors found (use design tokens)'; exit 1; else echo 'OK: no hardcoded hex colors in wizard/atoms/chrome'; fi"
   },
   "private": true,
   "packageManager": "npm@11.12.1",
@@ -26,23 +27,24 @@
     "tslib": "^2.3.0"
   },
   "devDependencies": {
+    "@angular-devkit/architect": "^0.2200.0",
+    "@angular-devkit/build-angular": "^22.0.0",
+    "@angular-devkit/core": "^22.0.0",
     "@angular/build": "^22.0.4",
     "@angular/cli": "^22.0.4",
     "@angular/compiler-cli": "^22.0.0",
-    "jsdom": "^29.0.0",
-    "prettier": "^3.8.1",
-    "typescript": "~6.0.2",
-    "vitest": "^4.0.8",
-    "storybook": "^10.4.6",
-    "@storybook/angular": "^10.4.6",
+    "@angular/platform-browser-dynamic": "^22.0.0",
+    "@compodoc/compodoc": "^1.2.1",
     "@storybook/addon-a11y": "^10.4.6",
     "@storybook/addon-docs": "^10.4.6",
     "@storybook/addon-onboarding": "^10.4.6",
-    "@angular-devkit/build-angular": "^22.0.0",
-    "@angular-devkit/architect": "^0.2200.0",
-    "@angular-devkit/core": "^22.0.0",
-    "@angular/platform-browser-dynamic": "^22.0.0",
-    "@compodoc/compodoc": "^1.2.1"
+    "@storybook/angular": "^10.4.6",
+    "jsdom": "^29.0.0",
+    "nswag": "^14.7.1",
+    "prettier": "^3.8.1",
+    "storybook": "^10.4.6",
+    "typescript": "~6.0.2",
+    "vitest": "^4.0.8"
   },
   "comment-overrides": "Pin patched versions of vulnerable DEV/BUILD-only transitive deps (Storybook + build chain). The shipped app already audits clean; this clears the dev-tooling advisories without downgrading Angular 22.",
   "overrides": {