LanguageMarker

This update focuses on a major internal cleanup and codebase restructuring without changing the addon's core feature set.

### Highlights

- Split large monolithic logic into clearer modules for core helpers, player/guild data handling, and UI hooks
- Cleaned up settings code and unified repeated UI patterns for dropdowns, checkboxes, and list rendering
- Standardized add/remove/edit flows for known players, custom auto-detect words, and guild assignments
- Improved internal consistency for shared APIs used by auto-detection, sync, and options panels
- Polished several localization strings and cleaned up mixed-language leftovers

### Technical cleanup

- Extracted player and guild storage logic into dedicated data handling code
- Moved tooltip, chat, context menu, and guild WHO marking hooks into their own UI-focused module
- Reduced duplicate implementations for language validation, feedback messages, and list management
- Improved naming and readability across the refactored files
- Added light documentation comments where behavior was not immediately obvious

### Compatibility

- No intentional feature removals
- No saved variable reset
- Existing player and guild assignments should continue to work as before

### Notes

This is primarily a maintenance and quality release. From a user perspective, LanguageMarker should feel familiar, but the addon is now much easier to maintain and extend going forward.