Add motion detection to camera server

🔍 New features:
- motion.py: Frame differencing motion detector
- Background thread compares frames continuously
- Configurable threshold, cooldown, sensitivity
- POSTs events + snapshot to collector

📡 New endpoints:
- GET /motion/stats - Detection statistics
- POST /motion/enable - Start detection
- POST /motion/disable - Stop detection

⚙️ Configuration (in .env):
- MOTION_ENABLED: true/false
- MOTION_THRESHOLD: Pixel diff threshold
- MOTION_COOLDOWN: Seconds between events
- COLLECTOR_URL: Where to POST events

Next: Event collector in vixy-mcp 🦊

server/requirements.txt

@@ -1,11 +1,14 @@
-# Camera Snapshot Server Dependencies
+# vixy-vision Server Requirements
 
 # Web framework
-fastapi>=0.104.0
-uvicorn[standard]>=0.24.0
+fastapi>=0.100.0
+uvicorn[standard]>=0.22.0
 
-# Camera access
+# Camera / CV
 opencv-python-headless>=4.8.0
 
-# Configuration
+# Config
 python-dotenv>=1.0.0
+
+# HTTP client (for posting events to collector)
+httpx>=0.24.0