fix(proxy): resolve 404 error and auto-setup proxy targets

Issues fixed:
1. Route prefix mismatch - Live config was set to use /claude, /codex,
   /gemini prefixes but server only had routes without prefixes
2. Proxy targets not auto-configured - start_with_takeover only modified
   Live config but didn't set is_proxy_target=true for current providers

Changes:
- Add prefixed routes (/claude/v1/messages, /codex/v1/*, /gemini/v1beta/*)
  to server.rs for backward compatibility
- Remove URL prefixes from takeover_live_configs() - server can route
  by API endpoint path alone (/v1/messages=Claude, /v1/chat/completions=Codex)
- Add setup_proxy_targets() method that automatically sets current providers
  as proxy targets when starting proxy with takeover
- Unify proxy toggle in SettingsPage to use takeover mode (same as main UI)
- Fix error message extraction in useProxyStatus hooks
- Fix provider switch logic to check both takeover flag AND proxy running state

src/App.tsx

@@ -33,6 +33,7 @@ import { ConfirmDialog } from "@/components/ConfirmDialog";
 import { SettingsPage } from "@/components/settings/SettingsPage";
 import { UpdateBadge } from "@/components/UpdateBadge";
 import { EnvWarningBanner } from "@/components/env/EnvWarningBanner";
+import { ProxyToggle } from "@/components/proxy/ProxyToggle";
 import UsageScriptModal from "@/components/UsageScriptModal";
 import UnifiedMcpPanel from "@/components/mcp/UnifiedMcpPanel";
 import PromptPanel from "@/components/prompts/PromptPanel";
@@ -63,7 +64,7 @@ function App() {
     "bg-orange-500 hover:bg-orange-600 dark:bg-orange-500 dark:hover:bg-orange-600 text-white shadow-lg shadow-orange-500/30 dark:shadow-orange-500/40 rounded-full w-8 h-8";
 
   // 获取代理服务状态
-  const { isRunning: isProxyRunning } = useProxyStatus();
+  const { isRunning: isProxyRunning, isTakeoverActive } = useProxyStatus();
 
   // 获取供应商列表，当代理服务运行时自动刷新
   const { data, isLoading, refetch } = useProvidersQuery(activeApp, {
@@ -321,6 +322,7 @@ function App() {
                   appId={activeApp}
                   isLoading={isLoading}
                   isProxyRunning={isProxyRunning}
+                  isProxyTakeover={isProxyRunning && isTakeoverActive}
                   onSwitch={switchProvider}
                   onEdit={setEditingProvider}
                   onDelete={setConfirmDelete}
@@ -482,6 +484,8 @@ function App() {
             )}
             {currentView === "providers" && (
               <>
+                <ProxyToggle />
+
                 <AppSwitcher activeApp={activeApp} onSwitch={setActiveApp} />
 
                 <div className="bg-muted p-1 rounded-xl flex items-center gap-1">