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>

src/styles.scss

@@ -7,6 +7,31 @@
 
 html, body { margin: 0; min-height: 100%; }
 
+/* App theme layer: a few app-specific measures RHC has no token for (content/form
+   widths), defined ONCE here and mapped onto RHC where possible. Components reference
+   these tokens instead of raw values. */
+:root {
+  --app-content-max: 64rem;                              /* readable page column */
+  --app-form-max: 30rem;                                 /* default wizard form width */
+  --app-form-narrow: 32rem;                              /* page-shell narrow variant */
+  --app-skip-link-offset: -999px;                        /* off-screen skip link */
+}
+
+/* App utility classes: centralise the repeated inline layout idioms so components stay
+   token-based and free of raw values. */
+.app-form { max-inline-size: var(--app-form-max); }
+.app-button-row {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--rhc-space-max-md);
+  align-items: center;
+}
+.app-button-row--spaced { margin-block-start: var(--rhc-space-max-xl); }
+/* vertical rhythm between stacked blocks */
+.app-stack > * + * { margin-block-start: var(--rhc-space-max-xl); }
+.app-section { margin-block-start: var(--rhc-space-max-2xl); }
+.app-text-subtle { color: var(--rhc-color-foreground-subtle); }
+
 /* Route transitions (withViewTransitions): cross-fade the routed CONTENT only.
    The chrome gets its own stable view-transition-name so it's lifted out of the
    `root` snapshot and stays put while the content fades. */