refactor(proxy): simplify provider selection to use is_current directly

Changes:
- Modify provider_router to select provider based on is_current flag
  instead of is_proxy_target queue
- Remove proxy target toggle UI from ProviderCard
- Remove proxyPriority and allProviders props from ProviderList
- Remove isProxyTarget prop from ProviderHealthBadge
- Use start_with_takeover() for auto-start to ensure proper setup

This simplifies the proxy architecture by directly using the current
provider for proxying, eliminating the need for separate proxy target
management. Switching providers now immediately takes effect in proxy
mode.

src/components/providers/ProviderList.tsx

@@ -5,7 +5,6 @@ import {
   useSortable,
   verticalListSortingStrategy,
 } from "@dnd-kit/sortable";
-import { useMemo } from "react";
 import type { CSSProperties } from "react";
 import type { Provider } from "@/types";
 import type { AppId } from "@/lib/api";
@@ -53,27 +52,6 @@ export function ProviderList({
   // 模型测试
   const { testProvider, isTesting } = useModelTest(appId);
 
-  // 计算代理目标的实际优先级映射 (P1, P2, P3...)
-  const proxyPriorityMap = useMemo(() => {
-    // 获取所有启用代理目标的供应商
-    const proxyTargets = sortedProviders.filter((p) => p.isProxyTarget);
-
-    // 按 sortIndex 排序
-    const sortedTargets = proxyTargets.sort((a, b) => {
-      const indexA = a.sortIndex ?? Number.MAX_SAFE_INTEGER;
-      const indexB = b.sortIndex ?? Number.MAX_SAFE_INTEGER;
-      return indexA - indexB;
-    });
-
-    // 创建优先级映射
-    const map = new Map<string, number>();
-    sortedTargets.forEach((provider, index) => {
-      map.set(provider.id, index + 1); // P1, P2, P3...
-    });
-
-    return map;
-  }, [sortedProviders]);
-
   const handleTest = (provider: Provider) => {
     testProvider(provider.id, provider.name);
   };
@@ -125,8 +103,6 @@ export function ProviderList({
               isTesting={isTesting(provider.id)}
               isProxyRunning={isProxyRunning}
               isProxyTakeover={isProxyTakeover}
-              proxyPriority={proxyPriorityMap.get(provider.id)}
-              allProviders={sortedProviders}
             />
           ))}
         </div>
@@ -149,8 +125,6 @@ interface SortableProviderCardProps {
   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
 }
 
 function SortableProviderCard({
@@ -167,8 +141,6 @@ function SortableProviderCard({
   isTesting,
   isProxyRunning,
   isProxyTakeover,
-  proxyPriority,
-  allProviders,
 }: SortableProviderCardProps) {
   const {
     setNodeRef,
@@ -202,8 +174,6 @@ function SortableProviderCard({
         isTesting={isTesting}
         isProxyRunning={isProxyRunning}
         isProxyTakeover={isProxyTakeover}
-        proxyPriority={proxyPriority}
-        allProviders={allProviders}
         dragHandleProps={{
           attributes,
           listeners,