Fix Python 3.11+ deprecation warnings

Issue: CI tests showed deprecation warnings for datetime.utcnow() and
SQLAlchemy declarative_base imports that will be removed in future versions.

Changes:
1. Replace datetime.utcnow() with datetime.now(timezone.utc).replace(tzinfo=None)
   - Using timezone.utc instead of UTC constant for Python 3.10 compatibility
   - Strip timezone info to maintain naive datetimes for SQLite compatibility
   - Updated in recording_service.py, api_recording.py, and recording.py models

2. Update SQLAlchemy declarative_base import
   - Changed from: from sqlalchemy.ext.declarative import declarative_base
   - Changed to: from sqlalchemy.orm import declarative_base
   - Fixed MovedIn20Warning in database/__init__.py

Impact: Eliminates 136 deprecation warnings in test output while maintaining
backward compatibility with existing database records.

Testing: All 85 tests pass successfully with no deprecation warnings for
these specific issues.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: MarkoVcode

benchmesh-serial-service/src/benchmesh_service/api_recording.py

@@ -8,7 +8,7 @@
 import csv
 import io
 from typing import List, Optional
-from datetime import datetime
+from datetime import datetime, timezone
 
 from fastapi import APIRouter, Depends, HTTPException, WebSocket, WebSocketDisconnect
 from fastapi.responses import StreamingResponse
@@ -184,7 +184,7 @@ async def list_recordings(db: Session = Depends(get_db)):
                 total_duration = (s.end_time - s.start_time).total_seconds() - s.pause_duration_seconds
             else:
                 # Recording active: use current time
-                total_duration = (datetime.utcnow() - s.start_time).total_seconds() - s.pause_duration_seconds
+                total_duration = (datetime.now(timezone.utc).replace(tzinfo=None) - s.start_time).total_seconds() - s.pause_duration_seconds
 
             recordings.append({
                 "id": s.id,
@@ -216,7 +216,7 @@ async def get_recording(series_id: int, db: Session = Depends(get_db)):
         if series.end_time:
             total_duration = (series.end_time - series.start_time).total_seconds() - series.pause_duration_seconds
         else:
-            total_duration = (datetime.utcnow() - series.start_time).total_seconds() - series.pause_duration_seconds
+            total_duration = (datetime.now(timezone.utc).replace(tzinfo=None) - series.start_time).total_seconds() - series.pause_duration_seconds
 
         return {
             "series": {

benchmesh-serial-service/src/benchmesh_service/database/__init__.py

@@ -10,8 +10,7 @@
 
 from sqlalchemy import create_engine, event
 from sqlalchemy.engine import Engine
-from sqlalchemy.ext.declarative import declarative_base
-from sqlalchemy.orm import sessionmaker, Session
+from sqlalchemy.orm import declarative_base, sessionmaker, Session
 
 from .config import get_database_url, DATABASE_CONFIG
 

benchmesh-serial-service/src/benchmesh_service/models/recording.py

@@ -4,7 +4,7 @@
 These models support multi-device recording with pause/resume functionality.
 """
 
-from datetime import datetime
+from datetime import datetime, timezone
 from sqlalchemy import Column, Integer, String, Text, Float, DateTime, ForeignKey
 from sqlalchemy.orm import relationship
 
@@ -30,8 +30,8 @@ class RecordingSeries(Base):
     paused_at = Column(DateTime)  # NULL if not paused
     pause_duration_seconds = Column(Float, default=0)  # Total time spent paused
     data_points_count = Column(Integer, default=0)
-    created_at = Column(DateTime, default=datetime.utcnow)
-    updated_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc).replace(tzinfo=None))
+    updated_at = Column(DateTime, default=lambda: datetime.now(timezone.utc).replace(tzinfo=None), onupdate=lambda: datetime.now(timezone.utc).replace(tzinfo=None))
 
     # Relationship to data points
     data_points = relationship(

benchmesh-serial-service/src/benchmesh_service/services/recording_service.py

@@ -7,7 +7,7 @@
 
 import asyncio
 import json
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Dict, List, Optional, Any, Set
 from sqlalchemy.orm import Session
 from fastapi import WebSocket
@@ -66,7 +66,7 @@ async def start_recording(
             description=description,
             interval_seconds=interval_seconds,
             channels=json.dumps(channels),
-            start_time=datetime.utcnow()
+            start_time=datetime.now(timezone.utc).replace(tzinfo=None)
         )
         db.add(series)
         db.commit()
@@ -111,7 +111,7 @@ async def pause_recording(self, db: Session, series_id: int) -> RecordingSeries:
         ).first()
 
         if series:
-            series.paused_at = datetime.utcnow()
+            series.paused_at = datetime.now(timezone.utc).replace(tzinfo=None)
             db.commit()
             db.refresh(series)
             logger.info(f"Paused recording: {series.name} (ID: {series_id})")
@@ -138,7 +138,7 @@ async def resume_recording(self, db: Session, series_id: int) -> RecordingSeries
         ).first()
 
         if series and series.paused_at:
-            pause_duration = (datetime.utcnow() - series.paused_at).total_seconds()
+            pause_duration = (datetime.now(timezone.utc).replace(tzinfo=None) - series.paused_at).total_seconds()
             series.pause_duration_seconds += pause_duration
             series.paused_at = None
             db.commit()
@@ -182,10 +182,10 @@ async def stop_recording(self, db: Session, series_id: int) -> RecordingSeries:
         ).first()
 
         if series:
-            series.end_time = datetime.utcnow()
+            series.end_time = datetime.now(timezone.utc).replace(tzinfo=None)
             # If still paused, add final pause duration
             if series.paused_at:
-                pause_duration = (datetime.utcnow() - series.paused_at).total_seconds()
+                pause_duration = (datetime.now(timezone.utc).replace(tzinfo=None) - series.paused_at).total_seconds()
                 series.pause_duration_seconds += pause_duration
                 series.paused_at = None
             db.commit()
@@ -337,7 +337,7 @@ async def _recording_loop(
                 # Store data point if we got any measurements
                 if measurements:
                     logger.info(f"[Series {series_id}] Collected {len(measurements)} measurements: {measurements}")
-                    timestamp = datetime.utcnow()
+                    timestamp = datetime.now(timezone.utc).replace(tzinfo=None)
 
                     with get_db_context() as db:
                         try: