feat: add test setup and fix related errors

[lucaspaiva-lp]

This PR introduces a proper test setup and fixes issues caused by shared database state during test execution.

What was done

• Added explicit test setup to ensure deterministic test behavior
• Fixed failing tests caused by accumulated data in the database
• Adjusted test logic to correctly validate repository behavior

Why

• Tests were failing because they relied on assumptions about database state.
• This change ensures tests behave predictably and reflect real system behavior.

Notes

• Tests currently run against a real SQLite database
• Data isolation is handled explicitly at the test level
• No changes were made to production logic