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.

vite.config.js

@@ -16,7 +16,7 @@ export default defineConfig({
                 'resources/js/player-data.js',
                 'resources/js/player.js',
                 'resources/js/playlist.js',
-                'resources/js/upload.js',
+                'resources/js/admin-release.js',
                 'resources/js/user-blacklist.js',
                 'resources/js/admin-edit.js',
                 'resources/js/admin-subtitles.js',