feat:實作 API 效能優化 — Redis 快取、分頁、DB 索引

- 引入 Redis（predis）快取層：Admin Stats（5分鐘）、課程列表（3分鐘，tag-based 失效）、評價分布（10分鐘）
- ReviewController::publicList 改為 paginate + eager load votes，消除 N+1
- AdminReviewController::index 加入分頁（預設 20，最大 100）
- 新增 notifications / diving_offers 效能索引 migration
- 新增 docker-compose.override.yml 本機開發 port mapping 機制（不進 git）

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

app/Http/Controllers/API/ProviderOfferController.php

@@ -5,6 +5,7 @@ namespace App\Http\Controllers\API;
 use App\Http\Controllers\Controller;
 use App\Models\DivingOffer;
 use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Cache;
 
 class ProviderOfferController extends Controller
 {
@@ -60,6 +61,8 @@ class ProviderOfferController extends Controller
 
         $offer = DivingOffer::create($validated);
 
+        Cache::tags(['diving_offers'])->flush();
+
         return response()->json(['status' => true, 'data' => $offer], 201);
     }
 
@@ -89,6 +92,8 @@ class ProviderOfferController extends Controller
 
         $offer->fill($validated)->save();
 
+        Cache::tags(['diving_offers'])->flush();
+
         return response()->json(['status' => true, 'data' => $offer]);
     }
 
@@ -106,6 +111,8 @@ class ProviderOfferController extends Controller
 
         $offer->delete();
 
+        Cache::tags(['diving_offers'])->flush();
+
         return response()->json(['status' => true, 'message' => '課程已刪除']);
     }
 }