feat(forms): add form_binding, form_subjects, form_filter_registry, form_builder configs

Groundwork for S2+ services. Entity Column Registry whitelists valid
Pattern A/C binding targets; subject-type registry enforces morph-map;
filter registry separates filterable columns from bindable ones; builder
config holds limits, webhook policy, captcha, retention, feature flags.
Adds dedicated 'webhooks' Redis queue connection (retry_after 120s).

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

api/config/form_subjects.php

@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+|--------------------------------------------------------------------------
+| Subject Type Registry
+|--------------------------------------------------------------------------
+|
+| Authoritative list of subject_type values permitted on form_submissions.
+| Must match morph-map keys registered in AppServiceProvider.
+|
+| 'permission_check' format: '<PolicyClass>@<method>' — invoked to authorise
+| access to a submission for this subject. Omit when policy doesn't exist yet.
+|
+*/
+
+return [
+
+    'person' => [
+        'model' => \App\Models\Person::class,
+        'display_attribute' => 'name',
+        'permission_check' => \App\Policies\PersonPolicy::class.'@view',
+    ],
+
+    'user' => [
+        'model' => \App\Models\User::class,
+        'display_attribute' => 'name',
+        // TODO: add permission_check when UserPolicy is built (S2)
+    ],
+
+    'company' => [
+        'model' => \App\Models\Company::class,
+        'display_attribute' => 'name',
+        'permission_check' => \App\Policies\CompanyPolicy::class.'@view',
+    ],
+
+    'organisation' => [
+        'model' => \App\Models\Organisation::class,
+        'display_attribute' => 'name',
+        'permission_check' => \App\Policies\OrganisationPolicy::class.'@view',
+    ],
+
+    'event' => [
+        'model' => \App\Models\Event::class,
+        'display_attribute' => 'name',
+        'permission_check' => \App\Policies\EventPolicy::class.'@view',
+    ],
+
+    // 'artist' entry added when artist module lands
+
+];