feat: pagination totals, request logging, data retention

Add shared paginate() helper with total count to all list endpoints.
Add request logging middleware (method, path, status, duration, IP).
Add data retention service with configurable thresholds and CLI command.

src/esp32_web/api/alerts.py

@@ -1,7 +1,7 @@
 """Alert endpoints."""
 from datetime import datetime, timedelta, UTC
 from flask import request
-from . import bp
+from . import bp, paginate
 from ..models import Alert
 from ..extensions import db
 
@@ -12,8 +12,6 @@ def list_alerts():
     alert_type = request.args.get('type')
     sensor_id = request.args.get('sensor_id', type=int)
     hours = request.args.get('hours', 24, type=int)
-    limit = min(int(request.args.get('limit', 100)), 1000)
-    offset = int(request.args.get('offset', 0))
 
     since = datetime.now(UTC) - timedelta(hours=hours)
     query = db.select(Alert).where(Alert.timestamp >= since).order_by(Alert.timestamp.desc())
@@ -23,7 +21,6 @@ def list_alerts():
     if sensor_id:
         query = query.where(Alert.sensor_id == sensor_id)
 
-    query = query.limit(limit).offset(offset)
-    alerts = db.session.scalars(query).all()
-
-    return {'alerts': [a.to_dict() for a in alerts], 'limit': limit, 'offset': offset}
+    result = paginate(query, Alert.to_dict)
+    return {'alerts': result['items'], 'total': result['total'],
+            'limit': result['limit'], 'offset': result['offset']}