fix: proxy_api_key from config not used in frontend or auth validation

/auth/status now returns config.server.proxy_api_key when set instead
of per-account random hash. validateProxyApiKey also accepts the
configured key.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/auth/account-pool.ts

@@ -331,6 +331,8 @@ export class AccountPool {
   }
 
   validateProxyApiKey(key: string): boolean {
+    const configKey = getConfig().server.proxy_api_key;
+    if (configKey && key === configKey) return true;
     for (const entry of this.accounts.values()) {
       if (entry.proxyApiKey === key) return true;
     }

src/routes/auth.ts

@@ -23,7 +23,8 @@ export function createAuthRoutes(
   app.get("/auth/status", (c) => {
     const authenticated = pool.isAuthenticated();
     const userInfo = pool.getUserInfo();
-    const proxyApiKey = pool.getProxyApiKey();
+    const config = getConfig();
+    const proxyApiKey = config.server.proxy_api_key ?? pool.getProxyApiKey();
     const summary = pool.getPoolSummary();
     return c.json({
       authenticated,