Implement logging functionality and update upload process with detailed logging

[AdeelTahir-SE]

This PR improves backend observability by introducing a centralized logging approach and adding meaningful logs across key request and task flows.

What I changed

1. Added a reusable logging utility module to standardize logging setup and usage.
2. Configured file-based application logging (with consistent log format).
3. Replaced scattered/basic logging calls with centralized helper functions.
4. Added contextual logs for major backend operations (upload flow, preferences, language settings, wikitext fetch, edit page flow).
5. Added task-level logs in async upload processing to track progress/failures.
6. Added exception logging in failure paths to capture stack traces and make debugging easier.