fix(provider): prevent case-insensitive name + key duplicates; migrate and startup dedupe

- Use case-insensitive compare for name + API key in migration
- Add runtime uniqueness checks in add/update commands
- Startup dedupe prefers current provider; archives others
- Keep original display casing; only normalize for comparisons
- Validate Codex config.toml as before; archive before overwrite

src-tauri/src/lib.rs

@@ -66,6 +66,11 @@ pub fn run() {
                 // 确保两个 App 条目存在
                 config_guard.ensure_app(&app_config::AppType::Claude);
                 config_guard.ensure_app(&app_config::AppType::Codex);
+                // 启动去重：名称(忽略大小写)+API Key
+                let removed = migration::dedupe_config(&mut *config_guard);
+                if removed > 0 {
+                    log::info!("已去重重复供应商 {} 个", removed);
+                }
             }
 
             // 保存配置