fix: correct rate limiting interval calculation in UIxMailEditor

The rate limiting check was using messageSubmissionBlockInterval (block duration)
instead of maximumSubmissionInterval (rate limit window) to determine if
message submission should be blocked.

Configuration example:
  SOGoMaximumMessageSubmissionCount: 5 messages
  SOGoMaximumRecipientCount: 100 recipients
  SOGoMaximumSubmissionInterval: 30 seconds (rate limit window)
  SOGoMessageSubmissionBlockInterval: 300 seconds (how long to block after violation)

Previous incorrect behavior:
  Code checked: delta <= block_time (<= 300s)
  Result: 5th message blocked even if sent AFTER 30s had elapsed

Correct behavior now:
  Code checks: delta < maximumSubmissionInterval (< 30s)
  Result: Only blocks if 5 messages sent WITHIN the 30s window

This also simplifies the counter reset logic - reset when the submission
interval has elapsed AND we're within limits.

Author: Tobias Weiß

UI/MailerUI/UIxMailEditor.m

@@ -875,8 +875,12 @@ - (WOResponse *) sendAction
       messages_count = [[messageSubmissions objectForKey: @"MessagesCount"] intValue];
       recipients_count =  [[messageSubmissions objectForKey: @"RecipientsCount"] intValue];
 
+      //
+      // Rate limit check: block if limits exceeded within the submission interval
+      // (not the block interval - that's for how long to block after a violation)
+      //
       if ((messages_count >= [dd maximumMessageSubmissionCount] || recipients_count >= [dd maximumRecipientCount]) &&
-          delta <= block_time)
+          delta < [dd maximumSubmissionInterval])
         {
           jsonResponse = [NSDictionary dictionaryWithObjectsAndKeys:
                                          @"failure", @"status",
@@ -887,8 +891,12 @@ - (WOResponse *) sendAction
                                 andString: [jsonResponse jsonRepresentation]];
         }
 
-      if (delta > block_time ||
-          (delta >= [dd maximumSubmissionInterval] && messages_count < [dd maximumMessageSubmissionCount] && recipients_count < [dd maximumRecipientCount]))
+      //
+      // Reset counters if the submission interval has elapsed AND we're within limits
+      //
+      if (delta >= [dd maximumSubmissionInterval] &&
+          messages_count < [dd maximumMessageSubmissionCount] &&
+          recipients_count < [dd maximumRecipientCount])
         {
           [[SOGoCache sharedCache] setMessageSubmissionsCount: 0
                                               recipientsCount: 0