feat: P1 보안/성능 개선 및 마이그레이션 자동화

Security fixes:
- migrate.ts: SQL/Command Injection 방지 (spawnSync 사용)
- migrate.ts: Path Traversal 검증 추가
- api-tester.ts: API 키 마스킹 (4자만 노출)
- api-tester.ts: 최소 16자 키 길이 검증
- cache.ts: ReDoS 방지 (패턴 길이/와일드카드 제한)

Performance improvements:
- cache.ts: 순차 삭제 → 병렬 배치 처리 (50개씩)
- cache.ts: KV 등록 fire-and-forget (non-blocking)
- cache.ts: 메모리 제한 (5000키)
- cache.ts: 25초 실행 시간 가드
- cache.ts: 패턴 매칭 prefix 최적화

New features:
- 마이그레이션 자동화 시스템 (scripts/migrate.ts)
- KV 기반 캐시 인덱스 (invalidatePattern, clearAll)
- 글로벌 CacheService 싱글톤

Other:
- .env.example 추가, API 키 환경변수 처리
- CACHE_TTL.RECOMMENDATIONS (10분) 분리
- e2e-tester.ts JSON 파싱 에러 핸들링 개선

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/routes/recommend.ts

@@ -8,7 +8,7 @@
 import type { Env, ScaleType } from '../types';
 import { RecommendationService } from '../services/recommendation';
 import { validateStack, STACK_REQUIREMENTS } from '../services/stackConfig';
-import { CacheService } from '../services/cache';
+import { getGlobalCacheService } from '../services/cache';
 import { logger } from '../utils/logger';
 import { HTTP_STATUS, CACHE_TTL, REQUEST_LIMITS } from '../constants';
 import {
@@ -33,23 +33,6 @@ interface RecommendRequestBody {
  */
 const SUPPORTED_SCALES: readonly ScaleType[] = ['small', 'medium', 'large'] as const;
 
-/**
- * Cached CacheService instance for singleton pattern
- */
-let cachedCacheService: CacheService | null = null;
-
-/**
- * Get or create CacheService singleton
- *
- * @returns CacheService instance with INSTANCES TTL
- */
-function getCacheService(): CacheService {
-  if (!cachedCacheService) {
-    cachedCacheService = new CacheService(CACHE_TTL.INSTANCES);
-  }
-  return cachedCacheService;
-}
-
 /**
  * Handle POST /recommend endpoint
  *
@@ -174,7 +157,7 @@ export async function handleRecommend(request: Request, env: Env): Promise<Respo
     // 7. Initialize cache service and generate cache key
     logger.info('[Recommend] Validation passed', { stack, scale, budgetMax });
 
-    const cacheService = getCacheService();
+    const cacheService = getGlobalCacheService(CACHE_TTL.RECOMMENDATIONS, env.RATE_LIMIT_KV);
 
     // Generate cache key from sorted stack, scale, and budget
     // Sort stack to ensure consistent cache keys regardless of order
@@ -224,7 +207,7 @@ export async function handleRecommend(request: Request, env: Env): Promise<Respo
         {
           status: HTTP_STATUS.OK,
           headers: {
-            'Cache-Control': `public, max-age=${CACHE_TTL.INSTANCES}`,
+            'Cache-Control': `public, max-age=${CACHE_TTL.RECOMMENDATIONS}`,
           },
         }
       );
@@ -258,7 +241,7 @@ export async function handleRecommend(request: Request, env: Env): Promise<Respo
 
     // 10. Store result in cache
     try {
-      await cacheService.set(cacheKey, responseData, CACHE_TTL.INSTANCES);
+      await cacheService.set(cacheKey, responseData, CACHE_TTL.RECOMMENDATIONS);
     } catch (error) {
       // Graceful degradation: log error but don't fail the request
       logger.error('[Recommend] Cache write failed',
@@ -273,7 +256,7 @@ export async function handleRecommend(request: Request, env: Env): Promise<Respo
       {
         status: HTTP_STATUS.OK,
         headers: {
-          'Cache-Control': `public, max-age=${CACHE_TTL.INSTANCES}`,
+          'Cache-Control': `public, max-age=${CACHE_TTL.RECOMMENDATIONS}`,
         },
       }
     );