fix(jobs): make throttle add/remove controls keyboard-accessible

Replace non-interactive span icons with real button elements so
throttle rows can be operated via keyboard and screen readers.

- app/Views/partial/job_throttles.php: swap add_throttle and
  remove_throttle spans for <button type="button"> elements,
  stripped of default border/background to preserve styling,
  with aria-label wired to new language strings.
- app/Language/en/Jobs.php: add add_throttle and remove_throttle
  labels used by the new aria-label attributes.

Signed-off-by: objecttothis <17935339+objecttothis@users.noreply.github.com>

app/Language/en/Jobs.php

@@ -1,6 +1,7 @@
 <?php
 
 return [
+    'add_throttle'                      => 'Add throttle',
     'mode'                              => 'Mode',
     'mode_auto'                         => 'Auto (Cron / Task Scheduler)',
     'mode_invalid'                      => 'Mode must be one of Auto, Web, or Manual.',
@@ -9,6 +10,7 @@ return [
     'not_yet_implemented'               => 'Not yet implemented — available in a future release.',
     'process_all_jobs'                  => 'Process All Jobs',
     'process_selected_jobs'             => 'Process Selected Jobs',
+    'remove_throttle'                   => 'Remove throttle',
     'saved_successfully'                => 'Job Queue settings saved successfully.',
     'saved_unsuccessfully'              => 'Job Queue settings could not be saved.',
     'select_jobs'                       => 'Select Jobs',

app/Views/partial/job_throttles.php

@@ -51,9 +51,9 @@ foreach ($throttles as $throttle) {
                     );
                     ?>
                 </div>
-                <span class="add_throttle glyphicon glyphicon-plus" style="flex: 0 0 auto; padding-left: 0.5em;"></span>
+                <button type="button" class="add_throttle glyphicon glyphicon-plus" style="flex: 0 0 auto; padding-left: 0.5em; border: none; background: none;" aria-label="<?= lang('Jobs.add_throttle') ?>"></button>
                 <span style="flex: 0 0 auto;">&nbsp;&nbsp;</span>
-                <span class="remove_throttle glyphicon glyphicon-minus" style="flex: 0 0 auto;"></span>
+                <button type="button" class="remove_throttle glyphicon glyphicon-minus" style="flex: 0 0 auto; border: none; background: none;" aria-label="<?= lang('Jobs.remove_throttle') ?>"></button>
             </div>
         </div>
     </div>