feat: add DEV_MODE configuration and implement dev-token endpoint for authentication

qwen3-tts-frontend/src/contexts/AuthContext.tsx

@@ -22,7 +22,15 @@ export function AuthProvider({ children }: { children: ReactNode }) {
   useEffect(() => {
     const initAuth = async () => {
       try {
-        const storedToken = localStorage.getItem('token')
+        let storedToken = localStorage.getItem('token')
+        if (!storedToken && import.meta.env.DEV) {
+          const res = await fetch('/api/auth/dev-token')
+          if (res.ok) {
+            const data = await res.json()
+            storedToken = data.access_token
+            localStorage.setItem('token', storedToken!)
+          }
+        }
         if (storedToken) {
           setToken(storedToken)
           const currentUser = await authApi.getCurrentUser()