feat: Restrict user-status endpoint to department members and chat partners

- Only return users from same department as current user
- Include users with existing private chat conversations
- Remove current user from results for privacy
- Improve performance by limiting user list

backend/app/main.py

@@ -6,7 +6,7 @@ from app.database import create_db_and_tables, get_session
 from app.config import get_settings
 from app.routers import auth, departments, channels, messages, files, websocket, snippets, admin, direct_messages, kanban
 from app.auth import get_current_user
-from app.models import User
+from app.models import User, DirectMessage, Department
 from sqlmodel import Session, select
 
 settings = get_settings()
@@ -79,23 +79,36 @@ def health_check():
 
 @app.get("/user-status")
 def get_user_statuses(session: Session = Depends(get_session), current_user: User = Depends(get_current_user)):
-    """Get online status for all users"""
+    """Get online status for users in same department and users with existing private chats"""
     from app.websocket import manager
     
-    # Get all users
-    statement = select(User)
-    users = session.exec(statement).all()
+    # Get users from same department
+    department_users = []
+    if current_user.departments:
+        dept_ids = [dept.id for dept in current_user.departments]
+        dept_statement = select(User).where(User.departments.any(Department.id.in_(dept_ids)))
+        department_users = session.exec(dept_statement).all()
+    
+    # Get users with existing private chats (either as sender or receiver)
+    chat_partners_statement = select(User).where(
+        (User.id == DirectMessage.sender_id) | (User.id == DirectMessage.receiver_id)
+    ).where(
+        (DirectMessage.sender_id == current_user.id) | (DirectMessage.receiver_id == current_user.id)
+    ).distinct()
+    chat_partners = session.exec(chat_partners_statement).all()
+    
+    # Combine and deduplicate users
+    all_users = list(set(department_users + chat_partners))
+    # Remove current user from the list
+    all_users = [user for user in all_users if user.id != current_user.id]
     
     # Get their statuses
     statuses = manager.get_all_user_statuses()
     
     # Build response
     result = []
-    for user in users:
+    for user in all_users:
         status = statuses.get(user.id, "offline")
-        # If user has no WebSocket connection but is the current user, mark as online
-        if status == "offline" and user.id == current_user.id:
-            status = "online"
         result.append({
             "user_id": user.id,
             "username": user.username,