Improve config.toml error reporting: point to the exact line with the issue

[alabulei1]

When there is an error in config.toml, the application always reports an error at line 1, even when the actual issue is located elsewhere in the file.

Example error message:

TOML parse error at line 1, column 1

However, this is misleading—the problem is not always on the first line. This makes debugging configuration issues unnecessarily difficult.

Expected behavior

• The error message should point to the exact line and column in config.toml where the problem occurs.
• If possible, include a brief description of what is wrong (e.g., invalid field, type mismatch, unknown key).

Why this matters
Accurate error locations would significantly improve the developer experience when editing or validating config.toml, especially as the configuration grows more complex.