Add branching intake wizard (derived steps + radio-group atom)

A second wizard demonstrating a BRANCHING flow: the visible steps are derived
from the answers by a pure `visibleSteps` function rather than stored, so
answering "buiten Nederland gewerkt? -> ja" or reporting few hours adds steps
and the progress denominator changes live. Same Elm-style store + RemoteData
patterns as the fixed wizard; answers persist to localStorage.

- intake.machine.ts: IntakeState union + Answers + visibleSteps + pure reduce (+spec)
- intake-wizard organism, intake.page, submit-intake command
- new radio-group atom (ControlValueAccessor) in shared/ui
- /intake route + dashboard link + concepts showcase section
- tighten Aantekening.type to a 'Specialisme' | 'Aantekening' union
- README + ARCHITECTURE updated

Verified live end-to-end (branches add steps 4->5->6, review, submit) with no
console errors; build, unit tests, and Storybook all green.

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

src/app/registratie/ui/dashboard.page.ts

@@ -61,6 +61,9 @@ import { BigProfileStore } from '@registratie/application/big-profile.store';
       <p>
         <app-link to="/herregistratie">Herregistratie aanvragen →</app-link>
       </p>
+      <p>
+        <app-link to="/intake">Herregistratie-intake (vragenlijst met vertakkingen) →</app-link>
+      </p>
       <p>
         <app-link to="/concepts">Functionele patronen (impossible states) →</app-link>
       </p>