feat(deployments): support Docker image tags for preview deployments

Add end-to-end support for `docker_registry_image_tag` in preview and deployment queue flows.

- Extend deploy API to accept `pull_request_id` alias and `docker_tag` for preview deploys
- Persist preview-specific Docker tags on `application_previews` and `application_deployment_queues`
- Pass tag through `queue_application_deployment()` and de-duplicate queued jobs by tag
- Update deployment job logic to resolve and use preview Docker tags for dockerimage build packs
- Update Livewire previews UI/state to manage per-preview tags and manual preview/tag inputs
- Add migration for new tag columns and model fillable/casts updates
- Add feature and unit tests covering API behavior and tag resolution

app/Models/ApplicationPreview.php

@@ -11,6 +11,7 @@ class ApplicationPreview extends BaseModel
     use SoftDeletes;
 
     protected $fillable = [
+        'application_id',
         'pull_request_id',
         'pull_request_html_url',
         'pull_request_issue_comment_id',
@@ -18,9 +19,14 @@ class ApplicationPreview extends BaseModel
         'status',
         'git_type',
         'docker_compose_domains',
+        'docker_registry_image_tag',
         'last_online_at',
     ];
 
+    protected $casts = [
+        'pull_request_id' => 'integer',
+    ];
+
     protected static function booted()
     {
         static::forceDeleting(function ($preview) {