优化：车辆违停和拥堵算法防频繁告警

违停：
- confirm_clear 30→120秒（持续2分钟无车才确认离开）
- cooldown 600→1800秒（30分钟冷却）
- ALARMED 清除阈值 ratio<0.3→ratio<0.15（更严格）

拥堵：
- confirm_clear 120→180秒
- cooldown 600→1800秒
- 消散阈值从 < threshold 改为 < threshold*0.5（降到一半才开始确认）

algorithms.py

@@ -747,8 +747,8 @@ class IllegalParkingAlgorithm:
         self,
         confirm_vehicle_sec: int = 15,
         parking_countdown_sec: int = 300,
-        confirm_clear_sec: int = 30,
-        cooldown_sec: int = 600,
+        confirm_clear_sec: int = 120,
+        cooldown_sec: int = 1800,
         target_classes: Optional[List[str]] = None,
         alarm_level: Optional[int] = None,
     ):
@@ -905,10 +905,10 @@ class IllegalParkingAlgorithm:
                     logger.debug(f"ROI {roi_id}: PARKED_COUNTDOWN → IDLE (冷却期内)")
 
         elif self.state == self.STATE_ALARMED:
-            if ratio < 0.3:
+            if ratio < 0.15:
                 self.state = self.STATE_CONFIRMING_CLEAR
                 self.state_start_time = current_time
-                logger.debug(f"ROI {roi_id}: ALARMED → CONFIRMING_CLEAR")
+                logger.debug(f"ROI {roi_id}: ALARMED → CONFIRMING_CLEAR (ratio={ratio:.2f}<0.15)")
 
         elif self.state == self.STATE_CONFIRMING_CLEAR:
             if self.state_start_time is None:
@@ -1002,8 +1002,8 @@ class VehicleCongestionAlgorithm:
         self,
         count_threshold: int = 5,
         confirm_congestion_sec: int = 60,
-        confirm_clear_sec: int = 120,
-        cooldown_sec: int = 600,
+        confirm_clear_sec: int = 180,
+        cooldown_sec: int = 1800,
         target_classes: Optional[List[str]] = None,
         alarm_level: Optional[int] = None,
     ):
@@ -1140,10 +1140,11 @@ class VehicleCongestionAlgorithm:
                     logger.debug(f"ROI {roi_id}: CONFIRMING_CONGESTION → NORMAL (冷却期内)")
 
         elif self.state == self.STATE_CONGESTED:
-            if avg_count < self.count_threshold:
+            # 车辆数降到阈值的一半以下才开始确认消散（避免抖动）
+            if avg_count < self.count_threshold * 0.5:
                 self.state = self.STATE_CONFIRMING_CLEAR
                 self.state_start_time = current_time
-                logger.debug(f"ROI {roi_id}: CONGESTED → CONFIRMING_CLEAR (avg={avg_count:.1f}<{self.count_threshold})")
+                logger.debug(f"ROI {roi_id}: CONGESTED → CONFIRMING_CLEAR (avg={avg_count:.1f}<{self.count_threshold * 0.5:.1f})")
 
         elif self.state == self.STATE_CONFIRMING_CLEAR:
             if self.state_start_time is None: