feat:영상 파일 GCS 저장 및 삭제 연동

- VideoGenerationJob: 최종 합성 후 GCS 업로드, gcs_path 저장
- Veo3Controller: download/preview GCS 서명URL 사용, destroy GCS 파일 삭제
- VideoGeneration 모델: gcs_path fillable 추가
- GCS 불가 시 로컬 파일로 폴백

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Jobs/VideoGenerationJob.php

@@ -8,6 +8,7 @@
 use App\Services\Video\TtsService;
 use App\Services\Video\VeoVideoService;
 use App\Services\Video\VideoAssemblyService;
+use App\Services\GoogleCloudStorageService;
 use Illuminate\Bus\Queueable;
 use Illuminate\Contracts\Queue\ShouldQueue;
 use Illuminate\Foundation\Bus\Dispatchable;
@@ -41,7 +42,8 @@ public function handle(
         VeoVideoService $veo,
         TtsService $tts,
         BgmService $bgm,
-        VideoAssemblyService $assembly
+        VideoAssemblyService $assembly,
+        GoogleCloudStorageService $gcs
     ): void {
         $video = VideoGeneration::withoutGlobalScopes()->find($this->videoGenerationId);
 
@@ -264,6 +266,28 @@ public function handle(
                 return;
             }
 
+            // === GCS 업로드 ===
+            $gcsPath = null;
+
+            if ($gcs->isAvailable()) {
+                $video->updateProgress(VideoGeneration::STATUS_ASSEMBLING, 95, 'GCS 업로드 중...');
+
+                $objectName = "video_gen/{$video->id}/final_{$video->id}.mp4";
+                $gcsUri = $gcs->upload($finalPath, $objectName);
+
+                if ($gcsUri) {
+                    $gcsPath = $objectName;
+                    Log::info('VideoGenerationJob: GCS 업로드 성공', [
+                        'id' => $video->id,
+                        'gcs_path' => $objectName,
+                    ]);
+                } else {
+                    Log::warning('VideoGenerationJob: GCS 업로드 실패, 로컬 파일로 계속', [
+                        'id' => $video->id,
+                    ]);
+                }
+            }
+
             // === 완료 ===
             $stepMsg = empty($skippedScenes)
                 ? '완료'
@@ -274,6 +298,7 @@ public function handle(
                 'progress' => 100,
                 'current_step' => $stepMsg,
                 'output_path' => $finalPath,
+                'gcs_path' => $gcsPath,
                 'cost_usd' => $totalCost,
             ]);
 
@@ -283,6 +308,7 @@ public function handle(
             Log::info('VideoGenerationJob: 영상 생성 완료', [
                 'id' => $video->id,
                 'output' => $finalPath,
+                'gcs_path' => $gcsPath,
                 'cost' => $totalCost,
             ]);
         } catch (\Exception $e) {