feat: auto activity logging on issue create/delete, fix schema db.add bug

app/services/activity.py

@@ -0,0 +1,18 @@
+"""Activity logging helper — auto-record CRUD operations."""
+import json
+from sqlalchemy.orm import Session
+from app.models.activity import ActivityLog
+
+
+def log_activity(db: Session, action: str, entity_type: str, entity_id: int, user_id: int = None, details: dict = None):
+    """Record an activity log entry."""
+    entry = ActivityLog(
+        action=action,
+        entity_type=entity_type,
+        entity_id=entity_id,
+        user_id=user_id,
+        details=json.dumps(details) if details else None,
+    )
+    db.add(entry)
+    db.commit()
+    return entry