feat(provider): integrate icon system into provider UI components

Add icon customization support to provider management interface:

## Type System Updates

### Provider Interface (src/types.ts)
- Add optional `icon` field for icon name (e.g., "openai", "anthropic")
- Add optional `iconColor` field for hex color (e.g., "#00A67E")

### Form Schema (src/lib/schemas/provider.ts)
- Extend providerSchema with icon and iconColor optional fields
- Maintain backward compatibility with existing providers

## UI Components

### ProviderCard (src/components/providers/ProviderCard.tsx)
- Display ProviderIcon alongside provider name
- Add icon container with hover animation effect
- Adjust layout spacing for icon placement
- Update translate offsets for action buttons

### BasicFormFields (src/components/providers/forms/BasicFormFields.tsx)
- Add icon preview section showing current selection
- Implement fullscreen icon picker dialog
- Auto-apply default color from icon metadata on selection
- Display provider name and icon status in preview

### AddProviderDialog & EditProviderDialog
- Pass icon fields through form submission
- Preserve icon data during provider updates

This enables users to visually distinguish providers in the list
with custom icons, improving UX for multi-provider setups.

src/types.ts

@@ -20,6 +20,9 @@ export interface Provider {
   isPartner?: boolean;
   // 可选：供应商元数据（仅存于 ~/.cc-switch/config.json，不写入 live 配置）
   meta?: ProviderMeta;
+  // 图标配置
+  icon?: string; // 图标名称（如 "openai", "anthropic"）
+  iconColor?: string; // 图标颜色（Hex 格式，如 "#00A67E"）
 }
 
 export interface AppConfig {