fix: force sample data insertion on database initialization

- Change init_db.py to use force_insert=True for sample data
- This ensures sample traces are always available even if detection logic fails
- Fixes issue where frontend shows non-existent trace IDs
- Resolves 404 errors when trying to process sample traces

backend/database/init_db.py

@@ -341,7 +341,7 @@ def init_database(reset=False, force=False):
             # Use SQLAlchemy session for sample data insertion
             session = SessionLocal()
             try:
-                results = insert_sample_data(session)
+                results = insert_sample_data(session, force_insert=True)
                 session.commit()
             except Exception as e:
                 session.rollback()