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.

database/migrations/2026_08_04_193201_add_validated_at_to_downloads_and_unique_slug_to_hentais.php

@@ -0,0 +1,36 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::table('downloads', function (Blueprint $table) {
+            $table->timestamp('validated_at')->nullable()->after('size');
+        });
+
+        Schema::table('hentais', function (Blueprint $table) {
+            $table->unique('slug');
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::table('hentais', function (Blueprint $table) {
+            $table->dropUnique(['slug']);
+        });
+
+        Schema::table('downloads', function (Blueprint $table) {
+            $table->dropColumn('validated_at');
+        });
+    }
+};