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>

public/mock/brp-address.json

@@ -1,8 +0,0 @@
-{
-  "gevonden": true,
-  "adres": {
-    "straat": "Lange Voorhout 9",
-    "postcode": "2514 EA",
-    "woonplaats": "Den Haag"
-  }
-}

public/mock/dashboard-view.json

@@ -1,23 +0,0 @@
-{
-  "registration": {
-    "bigNummer": "19012345601",
-    "naam": "Dr. A. (Anna) de Vries",
-    "beroep": "Arts",
-    "registratiedatum": "2012-09-01",
-    "geboortedatum": "1985-03-14",
-    "status": { "tag": "Geregistreerd", "herregistratieDatum": "2027-03-01" }
-  },
-  "person": {
-    "naam": "Dr. A. (Anna) de Vries",
-    "geboortedatum": "1985-03-14",
-    "adres": {
-      "straat": "Lange Voorhout 9",
-      "postcode": "2514 EA",
-      "woonplaats": "Den Haag"
-    }
-  },
-  "decisions": {
-    "eligibleForHerregistratie": true,
-    "herregistratieReason": "Registratie verloopt binnen 12 maanden (2027-03-01)."
-  }
-}

public/mock/duo-diplomas.json

@@ -1,38 +0,0 @@
-{
-  "diplomas": [
-    {
-      "id": "d1",
-      "naam": "Geneeskunde",
-      "instelling": "Universiteit Leiden",
-      "jaar": 2011,
-      "beroep": "Arts",
-      "policyQuestions": []
-    },
-    {
-      "id": "d2",
-      "naam": "Medicine (MBChB)",
-      "instelling": "University of Edinburgh",
-      "jaar": 2013,
-      "beroep": "Arts",
-      "policyQuestions": [
-        { "id": "nl-taalvaardigheid", "vraag": "Uw opleiding was Engelstalig. Beheerst u de Nederlandse taal op het vereiste niveau (B2)?", "type": "ja-nee" }
-      ]
-    },
-    {
-      "id": "d3",
-      "naam": "HBO-Verpleegkunde",
-      "instelling": "Hogeschool Utrecht",
-      "jaar": 2016,
-      "beroep": "Verpleegkundige",
-      "policyQuestions": []
-    }
-  ],
-  "handmatig": {
-    "beroepen": ["Arts", "Verpleegkundige", "Fysiotherapeut", "Apotheker", "Tandarts"],
-    "policyQuestions": [
-      { "id": "nl-taalvaardigheid", "vraag": "Beheerst u de Nederlandse taal op het vereiste niveau (B2)?", "type": "ja-nee" },
-      { "id": "diploma-erkend", "vraag": "Is uw diploma erkend door de Nederlandse overheid (bijv. via Nuffic)?", "type": "ja-nee" },
-      { "id": "toelichting", "vraag": "Geef een korte toelichting op uw diploma en opleiding.", "type": "tekst" }
-    ]
-  }
-}

public/mock/intake-policy.json

@@ -1 +0,0 @@
-{ "scholingThreshold": 1000 }

public/mock/notes.json

@@ -1,5 +0,0 @@
-[
-  { "type": "Specialisme", "omschrijving": "Huisartsgeneeskunde", "datum": "2016-04-12" },
-  { "type": "Aantekening", "omschrijving": "Erkend opleider huisartsgeneeskunde", "datum": "2019-01-08" },
-  { "type": "Specialisme", "omschrijving": "Spoedeisende hulp (kaderopleiding)", "datum": "2021-06-30" }
-]