cleanup: remove redundant sec_init_time_copy assignment in retry_security_if_needed

The local copy was being assigned 'now' immediately after setting the
shared state under mutex, but the subsequent retry check
(now - sec_init_time_copy) > SEC_RETRY_DELAY_MS is always false at
that point regardless, making the assignment a no-op. Added a comment
explaining why the copy is intentionally not updated.

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

Author: DerekSeaman

components/irk_capture/irk_capture.cpp

@@ -2661,7 +2661,9 @@ void IRKCaptureComponent::retry_security_if_needed(uint32_t now) {
     if (sec_init_time_copy == 0) {
       MutexGuard lock(state_mutex_);
       sec_init_time_ms_ = now;
-      sec_init_time_copy = now;
+      // sec_init_time_copy intentionally not updated: (now - now) == 0 which
+      // is always < SEC_RETRY_DELAY_MS, so the retry check below is a no-op
+      // on this iteration regardless.
     }
 
     // Retry security after configured delay