feat: block official provider switching during proxy takeover

Prevent users from switching to official providers (Anthropic/OpenAI/Google)
when proxy takeover is active, as using a proxy with official APIs may cause
account bans.

Defense-in-depth across 4 layers:
- Backend: ProviderService::switch(), hot_switch_provider(), switch_proxy_provider command
- Frontend: useProviderActions soft guard with error toast
- UI: ProviderActions button disabled with ShieldAlert icon
- Tray menu: official provider items disabled with ⛔ indicator

Also warns when enabling proxy takeover while current provider is official.

src-tauri/src/services/proxy.rs

@@ -15,6 +15,7 @@ use crate::services::provider::{
 use serde_json::{json, Value};
 use std::str::FromStr;
 use std::sync::Arc;
+use tauri::Emitter;
 use tokio::sync::RwLock;
 
 /// 用于接管 Live 配置时的占位符（避免客户端提示缺少 key，同时不泄露真实 Token）
@@ -375,6 +376,26 @@ impl ProxyService {
 
             // 7) 兼容旧逻辑：写入 any-of 标志（失败不影响功能）
             let _ = self.db.set_live_takeover_active(true).await;
+
+            // 8) Warn if the current provider is official (risk of account ban via proxy)
+            if let Ok(Some(current_id)) =
+                crate::settings::get_effective_current_provider(&self.db, &app)
+            {
+                if let Ok(Some(provider)) = self.db.get_provider_by_id(&current_id, app_type_str) {
+                    if provider.category.as_deref() == Some("official") {
+                        if let Some(handle) = self.app_handle.read().await.as_ref() {
+                            let _ = handle.emit(
+                                "proxy-official-warning",
+                                serde_json::json!({
+                                    "appType": app_type_str,
+                                    "providerName": provider.name,
+                                }),
+                            );
+                        }
+                    }
+                }
+            }
+
             return Ok(());
         }
 
@@ -1548,6 +1569,14 @@ impl ProxyService {
             .map_err(|e| format!("读取供应商失败: {e}"))?
             .ok_or_else(|| format!("供应商不存在: {provider_id}"))?;
 
+        // Defense-in-depth: block official providers during proxy takeover
+        if provider.category.as_deref() == Some("official") {
+            return Err(
+                "代理接管模式下不能切换到官方供应商 (Cannot switch to official provider during proxy takeover)"
+                    .to_string(),
+            );
+        }
+
         let logical_target_changed =
             crate::settings::get_effective_current_provider(&self.db, &app_type_enum)
                 .map_err(|e| format!("读取当前供应商失败: {e}"))?