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/components/providers/ProviderList.tsx

@@ -27,6 +27,7 @@ interface ProviderListProps {
   onCreate?: () => void;
   isLoading?: boolean;
   isProxyRunning?: boolean; // 代理服务运行状态
+  isProxyTakeover?: boolean; // 代理接管模式（Live配置已被接管）
 }
 
 export function ProviderList({
@@ -42,6 +43,7 @@ export function ProviderList({
   onCreate,
   isLoading = false,
   isProxyRunning = false, // 默认值为 false
+  isProxyTakeover = false, // 默认值为 false
 }: ProviderListProps) {
   const { sortedProviders, sensors, handleDragEnd } = useDragSort(
     providers,
@@ -122,6 +124,7 @@ export function ProviderList({
               onTest={handleTest}
               isTesting={isTesting(provider.id)}
               isProxyRunning={isProxyRunning}
+              isProxyTakeover={isProxyTakeover}
               proxyPriority={proxyPriorityMap.get(provider.id)}
               allProviders={sortedProviders}
             />
@@ -145,6 +148,7 @@ interface SortableProviderCardProps {
   onTest: (provider: Provider) => void;
   isTesting: boolean;
   isProxyRunning: boolean;
+  isProxyTakeover: boolean;
   proxyPriority?: number; // 代理目标的实际优先级 (1, 2, 3...)
   allProviders?: Provider[]; // 所有供应商列表
 }
@@ -162,6 +166,7 @@ function SortableProviderCard({
   onTest,
   isTesting,
   isProxyRunning,
+  isProxyTakeover,
   proxyPriority,
   allProviders,
 }: SortableProviderCardProps) {
@@ -196,6 +201,7 @@ function SortableProviderCard({
         onTest={onTest}
         isTesting={isTesting}
         isProxyRunning={isProxyRunning}
+        isProxyTakeover={isProxyTakeover}
         proxyPriority={proxyPriority}
         allProviders={allProviders}
         dragHandleProps={{