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>

api/app/Enums/EmailTemplateType.php

@@ -57,7 +57,7 @@ enum EmailTemplateType: string
             self::REGISTRATION_APPROVED => [
                 'subject' => 'Je registratie voor {event_name} is goedgekeurd!',
                 'heading' => 'Welkom aan boord!',
-                'body_text' => 'Goed nieuws! Je registratie als vrijwilliger voor {event_name} is goedgekeurd. Je kunt nu inloggen op het portaal om je diensten te bekijken en te claimen.',
+                'body_text' => 'Goed nieuws! Je registratie voor {event_name} is goedgekeurd. Klik op de knop hieronder om toegang te krijgen tot het portaal.',
                 'button_text' => 'Ga naar het portaal',
             ],
             self::REGISTRATION_REJECTED => [