fix(load): Add try/except/finally error handling to load function

[Satvik-Singh192]

Description

This pull request implements the error handling required by Issue #8 for the load function in app/etl/load.py.

It wraps the core database logic in a try...except...finally block. This change ensures that:

1. Any sqlite3.Error or general Exception during the database operation is caught.
2. The transaction is rolled back (conn.rollback()) if an error occurs, preventing partial or corrupt data writes.
3. The database connection (conn.close()) is always closed in the finally block, even if an error happens.

This resolves the "Error handling missing" and "Connection not closed properly" TODOs for this specific issue.

Semver Changes

• Patch (bug fix, no new features)
• Minor (new features, no breaking changes)
• Major (breaking changes)

Issues

Closes #8

Checklist

• I have read the Contributing Guidelines.