feat: runtime accent color picker with 6 presets

Replace all hardcoded #c8ff00 / rgba(200,255,0,...) with CSS custom
properties (--accent, --accent-rgb) so the accent color updates live.
Add themeStore (Zustand + localStorage) with 6 presets (Лайм, Синий,
Розовый, Фиолет, Оранж, Минт). Add ThemeApplier component that syncs
CSS vars on load. Add color picker UI section in ExtraTab.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/settings.local.json

@@ -60,7 +60,9 @@
       "Bash(git -C \"/d/!toyffee/party-mix-app/party-mix-app\" log --oneline -3)",
       "Bash(docker run *)",
       "Bash(docker exec *)",
-      "PowerShell(docker exec party-mix-app-web-1 *)"
+      "PowerShell(docker exec party-mix-app-web-1 *)",
+      "Bash(git add *)",
+      "Bash(git commit -m ' *)"
     ]
   }
 }