feat:AI 토큰 단가 설정 기능 추가 (DB 기반)

- ai_pricing_configs 테이블 마이그레이션 생성 (기본 시드 데이터 포함)
- AiPricingConfig 모델 추가 (캐시 적용 단가/환율 조회)
- AiReportService 하드코딩 단가를 DB 조회로 변경

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

app/Models/Tenants/AiPricingConfig.php

@@ -0,0 +1,67 @@
+<?php
+
+namespace App\Models\Tenants;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Support\Facades\Cache;
+
+class AiPricingConfig extends Model
+{
+    protected $table = 'ai_pricing_configs';
+
+    protected $fillable = [
+        'provider',
+        'model_name',
+        'input_price_per_million',
+        'output_price_per_million',
+        'unit_price',
+        'unit_description',
+        'exchange_rate',
+        'is_active',
+        'description',
+    ];
+
+    protected $casts = [
+        'input_price_per_million' => 'decimal:4',
+        'output_price_per_million' => 'decimal:4',
+        'unit_price' => 'decimal:6',
+        'exchange_rate' => 'decimal:2',
+        'is_active' => 'boolean',
+    ];
+
+    /**
+     * 활성 단가 설정 조회 (캐시 적용)
+     */
+    public static function getActivePricing(string $provider): ?self
+    {
+        return Cache::remember("ai_pricing_{$provider}", 3600, function () use ($provider) {
+            return self::where('provider', $provider)
+                ->where('is_active', true)
+                ->first();
+        });
+    }
+
+    /**
+     * 환율 조회 (첫 번째 활성 레코드 기준)
+     */
+    public static function getExchangeRate(): float
+    {
+        return Cache::remember('ai_pricing_exchange_rate', 3600, function () {
+            $config = self::where('is_active', true)->first();
+
+            return $config ? (float) $config->exchange_rate : 1400.0;
+        });
+    }
+
+    /**
+     * 캐시 초기화
+     */
+    public static function clearCache(): void
+    {
+        $providers = ['gemini', 'claude', 'google-stt', 'google-gcs'];
+        foreach ($providers as $provider) {
+            Cache::forget("ai_pricing_{$provider}");
+        }
+        Cache::forget('ai_pricing_exchange_rate');
+    }
+}

app/Services/AiReportService.php

@@ -2,6 +2,7 @@
 
 namespace App\Services;
 
+use App\Models\Tenants\AiPricingConfig;
 use App\Models\Tenants\AiReport;
 use App\Models\Tenants\AiTokenUsage;
 use App\Models\Tenants\Card;
@@ -398,12 +399,13 @@ private function saveTokenUsage(array $apiResult, string $model, string $menuNam
             $completionTokens = $usage['candidatesTokenCount'] ?? 0;
             $totalTokens = $usage['totalTokenCount'] ?? 0;
 
-            // Gemini 2.0 Flash 기준 단가 (USD per token)
-            $inputPricePerToken = 0.10 / 1_000_000;  // $0.10 / 1M tokens
-            $outputPricePerToken = 0.40 / 1_000_000;  // $0.40 / 1M tokens
+            // DB 단가 조회 (fallback: 하드코딩 기본값)
+            $pricing = AiPricingConfig::getActivePricing('gemini');
+            $inputPricePerToken = $pricing ? (float) $pricing->input_price_per_million / 1_000_000 : 0.10 / 1_000_000;
+            $outputPricePerToken = $pricing ? (float) $pricing->output_price_per_million / 1_000_000 : 0.40 / 1_000_000;
 
             $costUsd = ($promptTokens * $inputPricePerToken) + ($completionTokens * $outputPricePerToken);
-            $exchangeRate = (float) config('services.gemini.exchange_rate', 1400);
+            $exchangeRate = AiPricingConfig::getExchangeRate();
             $costKrw = $costUsd * $exchangeRate;
 
             AiTokenUsage::create([