fix(auth): remove username from password verification payload and fix proxy refresh handler

- Remove redundant username field from password verification payload in CodexAPIAuth
- Update proxy refresh button to use arrow function for proper event handling
- Simplify authentication flow by eliminating unnecessary email parameter in password verification request

backend/internal/auth/codex_api.go

@@ -492,7 +492,6 @@ func (c *CodexAPIAuth) ObtainAuthorizationCode() (string, error) {
 		verifyHeaders["OpenAI-Sentinel-Token"] = c.getSentinelHeader("password_verify")
 
 		passwordPayload := map[string]string{
-			"username": c.email,
 			"password": c.password,
 		}