feat(admin): rebuild release upload form with Livewire and CDN validation

Replace the server-rendered release upload form with a Livewire component,
introducing an interactive admin release form that supports dynamic episode
management, real‑time CDN path validation, and direct download file checks.

Key changes:
- New `AdminReleaseForm` Livewire component with dynamic episode fields,
  Tagify integration, and upload handling via Livewire's file uploads.
- Added `CdnPathValidator` service to verify download and stream paths across
  all configured mirrors, caching results and capturing file sizes.
- Extended `EpisodeService` and `GalleryService` to support array‑based data
  and temporary uploaded files from Livewire.
- Persist validated download sizes and store the validation timestamp on the
  `downloads` table via a new migration; also add a unique constraint on
  `hentais.slug` to prevent duplicates.
- Remove the old POST `/admin/release/upload` route and controller logic,
  along with the legacy `upload.js` script.
- Add comprehensive feature and unit tests covering the new component and the
  CDN validation service.

app/Services/DownloadService.php

@@ -33,4 +33,28 @@ class DownloadService
             }
         }
     }
+
+    /**
+     * Persist validated download URLs for an episode. Sizes are written
+     * directly from the CDN validation response, so no size job is dispatched.
+     *
+     * @param  array<string, array{url: string, size?: float|int|null}>  $downloads
+     */
+    public function createOrUpdateDownloadsFromArray(Episode $episode, array $downloads): void
+    {
+        foreach ($downloads as $type => $data) {
+            if (empty($data['url'])) {
+                continue;
+            }
+
+            Downloads::updateOrCreate([
+                'episode_id' => $episode->id,
+                'type' => $type,
+            ], [
+                'url' => $data['url'],
+                'size' => $data['size'] ?? null,
+                'validated_at' => now(),
+            ]);
+        }
+    }
 }