feat: add shared task assignments and quick win sorting

app/services/calendar_feeds.py

@@ -2,6 +2,8 @@ from __future__ import annotations
 
 from datetime import UTC, datetime, time, timedelta
 
+from sqlalchemy import or_
+
 from ..models import TaskInstance, User
 
 
@@ -23,7 +25,12 @@ def _format_timestamp(value: datetime | None) -> str:
 
 def build_calendar_feed(user: User, base_url: str) -> str:
     tasks = (
-        TaskInstance.query.filter_by(assigned_user_id=user.id)
+        TaskInstance.query.filter(
+            or_(
+                TaskInstance.assigned_user_id == user.id,
+                TaskInstance.assigned_user_secondary_id == user.id,
+            )
+        )
         .order_by(TaskInstance.due_date.asc(), TaskInstance.id.asc())
         .all()
     )