fix: 전체 시스템 감사 — 6건 수정 (보안 + 안정성)

Bug 1 (만료됨 스팸): Collector 시작 시 기존 pending skip
Bug 2 (pending 미삭제): Gateway에서 response 소비 시 pending도 삭제
Bug 3 (재시작 중복): Bug 1로 해결

Security 1: API 요청 1MB 크기 제한 (client_max_size)
Security 2: IP별 rate limiting (10 req/s)
Security 3: _commands 메모리 누수 방지 (TTL 30분)

collector.py

@@ -38,10 +38,17 @@ class CollectorBridge:
         self.remote = remote
         self.project_name = project_name
         self.event_queue = event_queue
-        self._forwarded_pending: set[str] = set()  # already forwarded request IDs
         self._poll_interval = 3  # seconds
         self._running = False
 
+        # Pre-populate with existing pending files → skip on startup (prevents 만료됨 spam)
+        self._forwarded_pending: set[str] = set()
+        for fname in self.local.list_json_files("pending"):
+            rid = fname.replace(".json", "")
+            self._forwarded_pending.add(rid)
+        if self._forwarded_pending:
+            logger.info(f"[COLLECTOR] skipping {len(self._forwarded_pending)} existing pending files")
+
     async def start(self):
         """Start the Collector polling loops."""
         self._running = True