fix: CameraRecord — reject negative entries/exits via Pydantic Field(ge=0)

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

server/camera_endpoint.py

@@ -11,14 +11,14 @@ import sqlite3
 from typing import List
 
 from fastapi import Depends
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 
 
 class CameraRecord(BaseModel):
     period_start: int
     period_end: int
-    entries: int
-    exits: int
+    entries: int = Field(ge=0)
+    exits: int = Field(ge=0)
 
 
 class CameraEventsRequest(BaseModel):