Add registratie wizard, BFF dashboard-view, contracts/value-objects, and architecture docs

Checkpoint of in-progress work: the registration wizard (address prefill,
DUO diploma lookup, policy questions), decision-DTO contracts, parse-don't-
validate value objects, infrastructure adapters, plus CLAUDE.md and the
architecture/ADR docs.

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

.storybook/preview.ts

@@ -14,6 +14,11 @@ const preview: Preview = {
   ],
   parameters: {
     layout: 'padded',
+    // Accessibility (axe) via @storybook/addon-a11y. Runs WCAG 2.0/2.1 A+AA rule
+    // sets on every story; flag violations in the a11y panel.
+    a11y: {
+      config: { runOnly: { type: 'tag', values: ['wcag2a', 'wcag2aa', 'wcag21a', 'wcag21aa'] } },
+    },
     controls: {
       matchers: {
         color: /(background|color)$/i,