feat(omo): integrate Oh My OpenCode profile management (#972)

* feat(omo): integrate Oh My OpenCode profile management into Provider system

Adds full-stack OMO support: backend config read/write/import, OMO-specific
provider CRUD with exclusive switching, frontend profile editor with
agent/category/model configuration, global config management, and i18n support.

* feat(omo): add model/variant dropdowns from enabled providers

Replace model text inputs with Select dropdowns sourced from enabled
OpenCode providers, add thinking-level variant selection, and prevent
auto-enabling newly added OMO providers.

* fix(omo): use standard provider action styles for OMO switch button

* fix(omo): replace hardcoded isZh strings with proper i18n t() calls

src/types.ts

@@ -3,7 +3,8 @@ export type ProviderCategory =
   | "cn_official" // 开源官方（原"国产官方"）
   | "aggregator" // 聚合网站
   | "third_party" // 第三方供应商
-  | "custom"; // 自定义
+  | "custom" // 自定义
+  | "omo"; // Oh My OpenCode
 
 export interface Provider {
   id: string;