feat(forms): add PHP enums for form builder

9 backed string enums covering purpose, field type, submission status/mode/review,
field width, value storage hint, snapshot mode, webhook delivery status.
FormPurpose/FormFieldType include helper methods per ARCH §3/§5. All with
declare(strict_types=1) and values() helpers for validation rules.

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

api/app/Enums/FormBuilder/FormPurpose.php

@@ -0,0 +1,119 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Enums\FormBuilder;
+
+enum FormPurpose: string
+{
+    case EVENT_REGISTRATION = 'event_registration';
+    case USER_PROFILE = 'user_profile';
+    case ARTIST_PROFILE = 'artist_profile';
+    case COMPANY_PROFILE = 'company_profile';
+    case ARTIST_ADVANCE = 'artist_advance';
+    case SUPPLIER_INTAKE = 'supplier_intake';
+    case INCIDENT_REPORT = 'incident_report';
+    case FEEDBACK = 'feedback';
+    case POST_EVENT_EVALUATION = 'post_event_evaluation';
+    case SIGNATURE_CONTRACT = 'signature_contract';
+    case SIGNATURE_CODE_OF_CONDUCT = 'signature_code_of_conduct';
+    case SIGNATURE_RECEIPT = 'signature_receipt';
+    case ABSENCE_REPORT = 'absence_report';
+    case CHECK_OUT_INVENTORY = 'check_out_inventory';
+    case PUBLIC_COMPLAINT = 'public_complaint';
+    case PUBLIC_PRESS_REQUEST = 'public_press_request';
+    case PUBLIC_RSVP = 'public_rsvp';
+    case ONBOARDING_WIZARD = 'onboarding_wizard';
+    case EVENT_SETUP_WIZARD = 'event_setup_wizard';
+    case COMPANY_CUSTOM = 'company_custom';
+    case ARTIST_CUSTOM = 'artist_custom';
+    case CUSTOM = 'custom';
+
+    /**
+     * @return array<int, string>
+     */
+    public static function values(): array
+    {
+        return array_map(fn (self $case): string => $case->value, self::cases());
+    }
+
+    /**
+     * Default subject_type for each purpose per ARCH §3.1.
+     * null = subject may be null (public or ambiguous).
+     */
+    public function defaultSubjectType(): ?string
+    {
+        return match ($this) {
+            self::EVENT_REGISTRATION,
+            self::POST_EVENT_EVALUATION,
+            self::SIGNATURE_RECEIPT,
+            self::ABSENCE_REPORT,
+            self::CHECK_OUT_INVENTORY => 'person',
+
+            self::USER_PROFILE,
+            self::SIGNATURE_CODE_OF_CONDUCT => 'user',
+
+            self::ARTIST_PROFILE,
+            self::ARTIST_ADVANCE,
+            self::ARTIST_CUSTOM => 'artist',
+
+            self::COMPANY_PROFILE,
+            self::SUPPLIER_INTAKE,
+            self::COMPANY_CUSTOM => 'company',
+
+            self::ONBOARDING_WIZARD => 'organisation',
+            self::EVENT_SETUP_WIZARD => 'event',
+
+            self::INCIDENT_REPORT,
+            self::FEEDBACK,
+            self::SIGNATURE_CONTRACT => 'user',
+
+            self::PUBLIC_COMPLAINT,
+            self::PUBLIC_PRESS_REQUEST,
+            self::PUBLIC_RSVP,
+            self::CUSTOM => null,
+        };
+    }
+
+    public function defaultSubmissionMode(): FormSubmissionMode
+    {
+        return match ($this) {
+            self::EVENT_REGISTRATION,
+            self::ARTIST_ADVANCE,
+            self::SUPPLIER_INTAKE => FormSubmissionMode::DRAFT_SINGLE,
+
+            self::INCIDENT_REPORT,
+            self::FEEDBACK,
+            self::SIGNATURE_RECEIPT,
+            self::ABSENCE_REPORT,
+            self::CHECK_OUT_INVENTORY,
+            self::PUBLIC_COMPLAINT,
+            self::PUBLIC_PRESS_REQUEST => FormSubmissionMode::MULTIPLE,
+
+            self::USER_PROFILE,
+            self::ARTIST_PROFILE,
+            self::COMPANY_PROFILE,
+            self::POST_EVENT_EVALUATION,
+            self::SIGNATURE_CONTRACT,
+            self::SIGNATURE_CODE_OF_CONDUCT,
+            self::PUBLIC_RSVP,
+            self::ONBOARDING_WIZARD,
+            self::EVENT_SETUP_WIZARD,
+            self::COMPANY_CUSTOM,
+            self::ARTIST_CUSTOM,
+            self::CUSTOM => FormSubmissionMode::SINGLE,
+        };
+    }
+
+    public function allowsPublicAccess(): bool
+    {
+        return match ($this) {
+            self::PUBLIC_COMPLAINT,
+            self::PUBLIC_PRESS_REQUEST,
+            self::PUBLIC_RSVP,
+            self::ARTIST_ADVANCE,
+            self::SUPPLIER_INTAKE => true,
+            default => false,
+        };
+    }
+}