perf: Merge library scanning with unlinked entry detection

[TheBobBobs]

Summary

Optimize the way unlinked entries are calculated and move logic into Library scanning since it can be quickly calculated with data from scan.

Scanning a library is now split into 3 steps.

1. Fetch all existing entry paths with ids. Collect into a dict[str, int] and set[str]
2. Using ripgrep or wcmatch get all valid files in library dir. Collect into set[str]
3. Use set operations to calculate which paths are new or missing.

If there are any missing paths the unlinked entries ui will be opened.
When the unlinked ui is closed new entries will automatically be saved if there are no remaining missing paths.

Tasks Completed

• Platforms Tested:
  • Windows x86
  • Linux x86
• Tested For:
  • Basic functionality