refactor(seeders): move DevSeeder to new form-builder structure

Adds UserObserver::created() that firstOrCreate's a user_profiles row
for every User. Registered in AppServiceProvider alongside PersonObserver.
Covers DevSeeder (3 scattered User::create sites: DatabaseSeeder super admin,
DevSeeder org staff, DevSeeder volunteer users) and all future creation
paths (invite/register/import) with zero per-caller boilerplate.

New FormBuilderDevSeeder seeder class holds canonical 16-field registration
template (borrowed from the legacy RegistrationFieldTemplateService list so
test data stays recognisable). Produces per-org:
- 16 form_templates (system, schema_snapshot per ARCH §4.6.1)
- 1 FormSchema per event (event_registration, owner=event, draft_single
  mode, is_published mirrors event.status lifecycle)
- 16 FormFields per schema
- 1 FormSubmission per person whose status ∈ applied/approved/no_show
  (same rule as MigrateLegacyFormsData), with 6 realistic FormValues each

DevSeeder::run() now wraps the whole seed body in
ActivityLog::suppressed(...) so the ~80 field creates + ~277 submission
lifecycle triggers don't flood activity_log. Also removes the legacy
RegistrationFieldTemplateService::seedSystemTemplates call — the 16
system templates now land directly in form_templates.

Post-seed totals (dev DB):
  5 form_schemas, 80 form_fields, 277 form_submissions, 1662 form_values,
  16 form_templates, 270 user_profiles (1:1 with users).

forms:verify-data-integrity on freshly seeded DB: exit 0.
php artisan test: 910/910.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/app/Providers/AppServiceProvider.php

@@ -38,6 +38,7 @@ use App\Models\FormBuilder\FormValue;
 use App\Models\VolunteerAvailability;
 use App\Observers\FormBuilder\FormValueObserver;
 use App\Observers\PersonObserver;
+use App\Observers\UserObserver;
 use Illuminate\Auth\Notifications\ResetPassword;
 use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Support\ServiceProvider;
@@ -97,6 +98,7 @@ class AppServiceProvider extends ServiceProvider
         ]);
 
         Person::observe(PersonObserver::class);
+        User::observe(UserObserver::class);
         FormValue::observe(FormValueObserver::class);
 
         ResetPassword::createUrlUsing(function ($user, string $token) {