feat: passwordless registration — defer account creation to approval

Removes password from the volunteer registration form. Account
creation is now deferred to the approval step:

Backend:
- Registration creates Person without User (user_id=null)
- On approval, system finds or creates User by person.email
- New accounts get a "set password" email with activation link
- Existing accounts get a portal link email
- Added registration_source column to persons (self/organizer)
- Fuzzy name matching skipped for self-registered persons
- person.email is always source of truth for account linking

Frontend:
- Registration form no longer collects password
- Email check shows info alert with login suggestion
- New wachtwoord-instellen.vue page for account activation
- PasswordRequirements.vue component (reused on reset page)
- Success page updated with activation messaging

Tests: 837 passed (all updated for new flow)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/portal/components.d.ts

@@ -43,6 +43,7 @@ declare module 'vue' {
     MoreBtn: typeof import('./src/@core/components/MoreBtn.vue')['default']
     Notifications: typeof import('./src/@core/components/Notifications.vue')['default']
     OverzichtTab: typeof import('./src/components/event/OverzichtTab.vue')['default']
+    PasswordRequirements: typeof import('./src/components/auth/PasswordRequirements.vue')['default']
     ProductDescriptionEditor: typeof import('./src/@core/components/ProductDescriptionEditor.vue')['default']
     RoosterTab: typeof import('./src/components/event/RoosterTab.vue')['default']
     RouterLink: typeof import('vue-router')['RouterLink']