Add placeholder content for empty content page (#37114)

- Empty repositories in organization

<img width="877" height="470" alt="image"
src="https://github.com/user-attachments/assets/94dc3992-1ab5-47cc-954a-8c420ec68500"
/>

- Empty projects in organization

<img width="1309" height="358" alt="image"
src="https://github.com/user-attachments/assets/94ef20c5-a6d9-4c39-9457-2a691a98d327"
/>

- Empty code search result in organization and global code search page

<img width="1312" height="345" alt="image"
src="https://github.com/user-attachments/assets/364f2a75-c68f-4302-b3b8-7ba1265622a1"
/>

- Empty worktime in organization

<img width="1301" height="357" alt="image"
src="https://github.com/user-attachments/assets/bb7f2cf8-fb95-463a-94c7-eafa63f56b2b"
/>

templates/shared/search/code/search.tmpl

@@ -24,6 +24,12 @@
 			{{template "shared/search/code/results" .}}
 		{{else if .Keyword}}
 			<div>{{ctx.Locale.Tr "search.no_results"}}</div>
+		{{else}}
+			<div class="empty-placeholder">
+				{{svg "octicon-search" 48}}
+				<h2>{{ctx.Locale.Tr "search.code_empty"}}</h2>
+				<p>{{ctx.Locale.Tr "search.code_empty_description"}}</p>
+			</div>
 		{{end}}
 	{{end}}
 </div>