refactor(auth): replace NextRefreshAfter with NextRetryAfter for clarity and consistency

- Renamed field `NextRefreshAfter` to `NextRetryAfter` across `AuthManager`, `types`, and selector logic.
- Updated references to ensure proper handling of retry timing logic.
- Improved code readability and clarified retry behavior for different auth states.

sdk/cliproxy/auth/selector.go

@@ -28,7 +28,7 @@ func (s *RoundRobinSelector) Pick(ctx context.Context, provider, model string, o
 	now := time.Now()
 	for i := range auths {
 		candidate := auths[i]
-		if candidate.Unavailable && candidate.Quota.NextRecoverAt.After(now) {
+		if candidate.Unavailable && candidate.NextRetryAfter.After(now) {
 			continue
 		}
 		if candidate.Status == StatusDisabled || candidate.Disabled {