feat(api): add frontend API and Query hooks for proxy config

Add TypeScript wrappers and TanStack Query hooks for:
- Global proxy config (address, port, logging)
- Per-app proxy config (failover, timeouts, circuit breaker)
- Proxy takeover status management

src/lib/api/index.ts

@@ -5,6 +5,7 @@ export { mcpApi } from "./mcp";
 export { promptsApi } from "./prompts";
 export { usageApi } from "./usage";
 export { vscodeApi } from "./vscode";
+export { proxyApi } from "./proxy";
 export * as configApi from "./config";
 export type { ProviderSwitchEvent } from "./providers";
 export type { Prompt } from "./prompts";