Refactor to manager-centric model, add team calendar for all users

Key changes:
- Removed office-centric model (deleted offices.py, office-rules)
- Renamed to team-rules, managers are part of their own team
- Team calendar visible to all (read-only for employees)
- Admins can have a manager assigned

database/connection.py

@@ -36,4 +36,7 @@ def get_db_session():
 def init_db():
     """Create all tables"""
     from database.models import Base
+
+    print(f"[init_db] Initializing database at {config.DATABASE_URL}")
     Base.metadata.create_all(bind=engine)
+    print(f"[init_db] Tables created: {list(Base.metadata.tables.keys())}")