feat: Implementiere umfassende RESTful API für LLM Gateway

Fügt 21 neue API-Endpoints in 4 Phasen hinzu:

Phase 1 - Foundation (Provider & Models):
- GET /api/providers - Liste aller Provider
- GET /api/providers/{provider} - Provider-Details
- GET /api/models - Liste aller Models mit Filtering/Sorting
- GET /api/models/{provider}/{model} - Model-Details

Phase 2 - Core Features (Credentials, Budget, Pricing):
- GET/POST/PUT/DELETE /api/credentials - Credential-Management
- POST /api/credentials/{id}/test - Connection Testing
- GET /api/budget - Budget-Status mit Projektionen
- GET /api/budget/history - Budget-Historie
- GET /api/pricing - Model-Pricing-Listen
- GET /api/pricing/calculator - Kosten-Kalkulator
- GET /api/pricing/compare - Preis-Vergleich

Phase 3 - Analytics (Usage Statistics):
- GET /api/usage/summary - Umfassende Statistiken
- GET /api/usage/requests - Request-History mit Pagination
- GET /api/usage/requests/{id} - Request-Details
- GET /api/usage/charts - Chart-Daten (4 Typen)

Phase 4 - Account (Account Info & Activity):
- GET /api/account - User-Informationen
- GET /api/account/activity - Activity-Log

Features:
- Vollständige Scramble/Swagger-Dokumentation
- Consistent Error-Handling
- API-Key Authentication
- Filtering, Sorting, Pagination
- Budget-Tracking mit Alerts
- Provider-Breakdown
- Performance-Metriken
- Chart-Ready-Data

Controller erstellt:
- ProviderController
- ModelController
- CredentialController
- BudgetController
- PricingController
- UsageController
- AccountController

Dokumentation:
- API_KONZEPT.md - Vollständiges API-Konzept
- API_IMPLEMENTATION_STATUS.txt - Implementation-Tracking
- API_IMPLEMENTATION_SUMMARY.md - Zusammenfassung und Workflows

laravel-app/routes/api.php

@@ -2,7 +2,16 @@
 
 use Illuminate\Http\Request;
 use Illuminate\Support\Facades\Route;
-use App\Http\Controllers\Api\ChatCompletionController;
+use App\Http\Controllers\Api\{
+    ChatCompletionController,
+    ProviderController,
+    ModelController,
+    CredentialController,
+    BudgetController,
+    PricingController,
+    UsageController,
+    AccountController
+};
 
 /*
 |--------------------------------------------------------------------------
@@ -15,12 +24,46 @@ use App\Http\Controllers\Api\ChatCompletionController;
 |
 */
 
-Route::middleware('auth:sanctum')->group(function () {
-    // Chat Completion Endpoint
+Route::middleware('auth:api')->group(function () {
+    // Provider Discovery Endpoints
+    Route::get('/providers', [ProviderController::class, 'index']);
+    Route::get('/providers/{provider}', [ProviderController::class, 'show']);
+    
+    // Model Discovery Endpoints
+    Route::get('/models', [ModelController::class, 'index']);
+    Route::get('/models/{provider}/{model}', [ModelController::class, 'show']);
+    
+    // Credentials Management Endpoints
+    Route::get('/credentials', [CredentialController::class, 'index']);
+    Route::post('/credentials', [CredentialController::class, 'store']);
+    Route::put('/credentials/{id}', [CredentialController::class, 'update']);
+    Route::delete('/credentials/{id}', [CredentialController::class, 'destroy']);
+    Route::post('/credentials/{id}/test', [CredentialController::class, 'test']);
+    
+    // Budget Management Endpoints
+    Route::get('/budget', [BudgetController::class, 'index']);
+    Route::get('/budget/history', [BudgetController::class, 'history']);
+    
+    // Pricing Endpoints
+    Route::get('/pricing', [PricingController::class, 'index']);
+    Route::get('/pricing/calculator', [PricingController::class, 'calculator']);
+    Route::get('/pricing/compare', [PricingController::class, 'compare']);
+    
+    // Usage Statistics Endpoints
+    Route::get('/usage/summary', [UsageController::class, 'summary']);
+    Route::get('/usage/requests', [UsageController::class, 'requests']);
+    Route::get('/usage/requests/{id}', [UsageController::class, 'show']);
+    Route::get('/usage/charts', [UsageController::class, 'charts']);
+    
+    // Account Information Endpoints
+    Route::get('/account', [AccountController::class, 'index']);
+    Route::get('/account/activity', [AccountController::class, 'activity']);
+    
+    // Chat Completion Endpoint - for gateway_users with API-Key authentication
     Route::post('/chat/completions', [ChatCompletionController::class, 'create'])
         ->middleware(['checkbudget', 'checkratelimit']);
     
-    // User info endpoint
+    // User info endpoint - returns GatewayUser
     Route::get('/user', function (Request $request) {
         return $request->user();
     });