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/ProviderCard.tsx

@@ -40,6 +40,7 @@ interface ProviderCardProps {
   onTest?: (provider: Provider) => void;
   isTesting?: boolean;
   isProxyRunning: boolean;
+  isProxyTakeover?: boolean; // 代理接管模式（Live配置已被接管，切换为热切换）
   proxyPriority?: number; // 代理目标的实际优先级 (1, 2, 3...)
   allProviders?: Provider[]; // 所有供应商列表，用于计算开启后的优先级
   dragHandleProps?: DragHandleProps;
@@ -93,6 +94,7 @@ export function ProviderCard({
   onTest,
   isTesting,
   isProxyRunning,
+  isProxyTakeover = false,
   proxyPriority,
   allProviders,
   dragHandleProps,
@@ -231,7 +233,12 @@ export function ProviderCard({
       className={cn(
         "relative overflow-hidden rounded-xl border border-border p-4 transition-all duration-300",
         "bg-card text-card-foreground group hover:border-border-active",
-        isCurrent ? "border-primary/50 shadow-sm" : "hover:shadow-sm",
+        // 代理接管模式下当前供应商使用绿色边框
+        isProxyTakeover && isCurrent
+          ? "border-emerald-500/60 shadow-sm shadow-emerald-500/10"
+          : isCurrent
+            ? "border-primary/50 shadow-sm"
+            : "hover:shadow-sm",
         dragHandleProps?.isDragging &&
           "cursor-grabbing border-primary shadow-lg scale-105 z-10",
       )}