feat: registration field polish, multi-category tags, file uploads, Partner icon

- Restructure field editor dialog: move Options section to bottom with
  divider and subheader, fix delete button with flex layout
- Change tag_category (single string) to tag_categories (JSON array)
  supporting multiple category selection in tag picker fields
- Portal tag picker now groups tags by category with subheaders
- Add generic file upload endpoint (FileUploadService + UploadController)
- Replace email branding logo URL text field with ImageUploadField
- Update Partner crowd type default icon to tabler-affiliate
- Apply changes consistently to both field and template dialogs

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

api/routes/api.php

@@ -38,6 +38,7 @@ use App\Http\Controllers\Api\V1\EmailChangeController;
 use App\Http\Controllers\Api\V1\PasswordResetController;
 use App\Http\Controllers\Api\V1\PortalMeController;
 use App\Http\Controllers\Api\V1\Portal\PortalShiftController;
+use App\Http\Controllers\Api\V1\UploadController;
 use App\Http\Controllers\Api\V1\UserOrganisationTagController;
 use App\Http\Controllers\Api\V1\Admin\AdminOrganisationController;
 use App\Http\Controllers\Api\V1\Admin\AdminUserController;
@@ -146,6 +147,9 @@ Route::middleware(['auth:sanctum', 'impersonation'])->group(function () {
     Route::delete('auth/trusted-devices/{device}', [TrustedDeviceController::class, 'destroy']);
     Route::delete('auth/trusted-devices', [TrustedDeviceController::class, 'destroyAll']);
 
+    // File uploads
+    Route::post('upload/image', [UploadController::class, 'uploadImage']);
+
     // Account management (self-service)
     Route::put('me/profile', [AccountController::class, 'updateProfile']);
     Route::post('me/change-password', [AccountController::class, 'changePassword']);