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-tauri/src/error.rs

@@ -52,6 +52,8 @@ pub enum AppError {
     },
     #[error("数据库错误: {0}")]
     Database(String),
+    #[error("OMO 配置文件不存在")]
+    OmoConfigNotFound,
     #[error("所有供应商已熔断，无可用渠道")]
     AllProvidersCircuitOpen,
     #[error("未配置供应商")]