Review of refactoring

[ry2x]

I did a review of #21 , and I found some problems with my documents.

In the parser.rs

1. Error handling weaknesses: When modmask parsing fails, the block is skipped by returning None. However, this makes it impossible to log or display in the UI the reason for the parsing failure.
2. Modmask magic numbers: Numeric values such as 0x40 and 0x08 are directly embedded. A more Rust-like implementation would be to define these as constants or use a library that handles bit flags.
3. Performance: Creating a HashMap and copying Strings each time can be an overhead for large configuration files.