Refactor AdminSettings into modular components

Split 1123-line monolithic AdminSettings.tsx into 11 modules:

Components:
- icons.tsx (85 lines) - All SVG icons
- Toggle.tsx (21 lines) - Reusable toggle component
- SettingInput.tsx (89 lines) - Text/select input for settings
- SettingRow.tsx (104 lines) - Single setting card
- BrandingTab.tsx (212 lines) - Logo, name, animation settings
- ThemeTab.tsx (277 lines) - Theme presets and custom colors
- FavoritesTab.tsx (59 lines) - Starred settings display
- SettingsTab.tsx (144 lines) - Accordion categories view

Utilities:
- constants.ts (55 lines) - MENU_SECTIONS, THEME_PRESETS
- utils.ts (35 lines) - formatSettingKey, stripHtml
- index.ts (13 lines) - Barrel exports

Result: AdminSettings.tsx reduced from 1123 to 251 lines

src/components/admin/SettingInput.tsx

@@ -0,0 +1,89 @@
+import { useState } from 'react'
+import { SettingDefinition } from '../../api/adminSettings'
+import { CheckIcon, CloseIcon } from './icons'
+
+interface SettingInputProps {
+  setting: SettingDefinition
+  onUpdate: (value: string) => void
+  disabled?: boolean
+}
+
+export function SettingInput({ setting, onUpdate, disabled }: SettingInputProps) {
+  const [isEditing, setIsEditing] = useState(false)
+  const [value, setValue] = useState('')
+
+  const handleStart = () => {
+    setValue(String(setting.current ?? ''))
+    setIsEditing(true)
+  }
+
+  const handleSave = () => {
+    onUpdate(value)
+    setIsEditing(false)
+  }
+
+  const handleCancel = () => {
+    setIsEditing(false)
+    setValue('')
+  }
+
+  // Dropdown for choices
+  if (setting.choices && setting.choices.length > 0) {
+    return (
+      <select
+        value={String(setting.current ?? '')}
+        onChange={(e) => onUpdate(e.target.value)}
+        disabled={disabled}
+        className="bg-dark-700 border border-dark-600 rounded-lg px-3 py-1.5 text-sm text-dark-100 focus:outline-none focus:border-accent-500 disabled:opacity-50"
+      >
+        {setting.choices.map((choice, idx) => (
+          <option key={idx} value={String(choice.value)}>
+            {choice.label}
+          </option>
+        ))}
+      </select>
+    )
+  }
+
+  // Editing mode
+  if (isEditing) {
+    return (
+      <div className="flex items-center gap-2">
+        <input
+          type={setting.type === 'int' || setting.type === 'float' ? 'number' : 'text'}
+          value={value}
+          onChange={(e) => setValue(e.target.value)}
+          onKeyDown={(e) => {
+            if (e.key === 'Enter') handleSave()
+            if (e.key === 'Escape') handleCancel()
+          }}
+          autoFocus
+          className="bg-dark-700 border border-accent-500 rounded-lg px-3 py-1.5 text-sm text-dark-100 focus:outline-none w-32"
+        />
+        <button
+          onClick={handleSave}
+          className="p-1.5 rounded-lg bg-accent-500 text-white hover:bg-accent-600 transition-colors"
+        >
+          <CheckIcon />
+        </button>
+        <button
+          onClick={handleCancel}
+          className="p-1.5 rounded-lg bg-dark-600 text-dark-300 hover:bg-dark-500 transition-colors"
+        >
+          <CloseIcon />
+        </button>
+      </div>
+    )
+  }
+
+  // Display mode
+  return (
+    <button
+      onClick={handleStart}
+      disabled={disabled}
+      className="bg-dark-700 border border-dark-600 rounded-lg px-3 py-1.5 text-sm text-dark-200 hover:border-dark-500 transition-colors disabled:opacity-50 min-w-[80px] text-left font-mono truncate max-w-[150px]"
+    >
+      {String(setting.current ?? '-')}
+    </button>
+  )
+}