feat: add color presets + fix badge hover effect

- Add global color presets: save/apply/delete sets of {bg, border, text}
  colors as reusable presets, shown as mini badges in their own colors.
- Popover: preset badges under preview with + to save, click to apply,
  × on hover to delete.
- Popup: dedicated Color Presets section with same functionality,
  applying to light subreddit badge colors.
- Storage: colorPresets array added to settings defaults.
- Fix badge hover: change brightness(0.9) to brightness(1.1) so hover
  brightens (activates) instead of dimming.

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/settings.js

@@ -17,6 +17,7 @@
     "dark.commentsBorderColor": "#888888",
     "dark.commentsTextColor": "#cccccc",
     subredditColors: {},
+    colorPresets: [],
   };
 
   function migrateSubredditColors(colors) {