Code Quality: Improve dashboard code and fix warnings

[mkh-user]

Summary

No behavior change or fix (tested), just fixes warnings like unused argument and shadowed name, and a small grammar fix. An unnecessary convert v if v is not None else "" was changed to v, and the misleading comment associated with it was corrected. Additionally, the unused debug parameter in dashboard/app.run() was marked for separate correction.

Details

Performed improvements:

• Prefixing with underscore to suppress unused variable warning
• Renaming to avoid shadowing
• Docstrings grammar fix
• Renaming import to follow naming conventions
• Converting to static method
• Removing redundant variable initialization
• Removing redundant parentheses in return statement
• Remove sentinel string replacement for None in sort key, rely on tuple ordering, Also clarify type-mismatch limits

---

Follow-Ups

• fenn/dashboard/app.py:335-347:

+# TODO: Use 'debug' in logger
def run(
    host: str = "127.0.0.1", port: int = 5000, debug: bool = False, log_dirs=None
) -> None:
    """Configure and start the dashboard server."""
    if log_dirs:
        scanner.add_dirs(log_dirs)
    logging.getLogger("werkzeug").setLevel(logging.ERROR)
    app.logger.setLevel(logging.ERROR)
    print(f"Fenn dashboard started at http://{host}:{port}")
    from werkzeug.serving import make_server
    make_server(host, port, app).serve_forever()

debug parameter is not used here, marked to catch later, proposed usage is:

log_level = logging.DEBUG if debug else logging.ERROR
logging.getLogger("werkzeug").setLevel(log_level)
app.logger.setLevel(log_level)

Is this change appropriate to create another PR for it?