Simple Guild Manager

Simple Guild Recruiter UI Refresh

- Updated the addon UI to match the new modern shared addon style.
- Replaced old Blizzard-style dialog and tooltip borders with clean flat 1px borders.
- Added a dark slate / blue-gray default theme for a cleaner professional look.
- Renamed the default silver theme to Modern Slate.
- Restyled the main window, compact widget, headers, tabs, buttons, inputs, scrollbars, and content panels.
- Updated recruitment scanner, invite queue, message editor, guild roster, guild alerts, stats, and options panels for a more consistent layout.
- Replaced old brass/gold hover highlights with cleaner theme-based hover and active states.
- Improved row styling for queue entries, saved messages, guild alerts, and roster lists.
- Updated custom color defaults to better match the new modern theme.