Show total TrackedTime on issue/pull/milestone lists (#26672)

TODOs:
- [x] write test for `GetIssueTotalTrackedTime`
- [x] frontport kitharas template changes and make them mobile-friendly

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![image](https://github.com/go-gitea/gitea/assets/24977596/6713da97-201f-4217-8588-4c4cec157171)

![image](https://github.com/go-gitea/gitea/assets/24977596/3a45aba8-26b5-4e6a-b97d-68bfc2bf9024)

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*Sponsored by Kithara Software GmbH*

templates/repo/issue/list.tmpl

@@ -34,6 +34,15 @@
 		<div id="issue-actions" class="issue-list-toolbar gt-hidden">
 			<div class="issue-list-toolbar-left">
 				{{template "repo/issue/openclose" .}}
+				<!-- Total Tracked Time -->
+				{{if .TotalTrackedTime}}
+					<div class="ui compact tiny secondary menu">
+						<span class="item" data-tooltip-content='{{ctx.Locale.Tr "tracked_time_summary"}}'>
+							{{svg "octicon-clock"}}
+							{{.TotalTrackedTime | Sec2Time}}
+						</span>
+					</div>
+				{{end}}
 			</div>
 			<div class="issue-list-toolbar-right">
 				{{template "repo/issue/filter_actions" .}}