Refactor theme settings with two collapsible sections

- Quick Presets: collapsible section with 8 theme presets
- Custom Colors: collapsible section with all color pickers
- Added translations for quickPresets, customColors in all locales (ru, en, zh, fa)
- Chevron icon rotates when section is expanded
- Preview section moved inside Custom Colors

src/locales/en.json

@@ -1221,6 +1221,10 @@
   "theme": {
     "colors": "Theme Colors",
     "reset": "Reset",
+    "quickPresets": "Quick Presets",
+    "quickPresetsDescription": "Choose a ready-made color scheme",
+    "customColors": "Custom Colors",
+    "customColorsDescription": "Customize each color individually",
     "accent": "Accent Color",
     "accentDescription": "Main brand color for buttons, links and interactive elements",
     "darkTheme": "Dark Theme",

src/locales/fa.json

@@ -700,6 +700,10 @@
   "theme": {
     "colors": "رنگ‌های تم",
     "reset": "بازنشانی",
+    "quickPresets": "پیش‌تنظیمات سریع",
+    "quickPresetsDescription": "یک طرح رنگی آماده انتخاب کنید",
+    "customColors": "رنگ‌های سفارشی",
+    "customColorsDescription": "هر رنگ را جداگانه سفارشی کنید",
     "accent": "رنگ تأکیدی",
     "accentDescription": "رنگ اصلی برند برای دکمه‌ها، لینک‌ها و عناصر تعاملی",
     "darkTheme": "تم تیره",

src/locales/ru.json

@@ -1379,6 +1379,10 @@
   "theme": {
     "colors": "Цвета темы",
     "reset": "Сбросить",
+    "quickPresets": "Быстрые пресеты",
+    "quickPresetsDescription": "Выберите готовую цветовую схему",
+    "customColors": "Ручная настройка",
+    "customColorsDescription": "Настройте каждый цвет отдельно",
     "accent": "Акцентный цвет",
     "accentDescription": "Основной цвет бренда для кнопок, ссылок и интерактивных элементов",
     "darkTheme": "Тёмная тема",

src/locales/zh.json

@@ -701,6 +701,10 @@
   "theme": {
     "colors": "主题颜色",
     "reset": "重置",
+    "quickPresets": "快速预设",
+    "quickPresetsDescription": "选择现成的配色方案",
+    "customColors": "自定义颜色",
+    "customColorsDescription": "单独自定义每种颜色",
     "accent": "主题色",
     "accentDescription": "用于按钮、链接和交互元素的主品牌颜色",
     "darkTheme": "深色主题",