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"
/>

options/locale/locale_en-US.json

@@ -173,6 +173,8 @@
   "search.org_kind": "Search orgs…",
   "search.team_kind": "Search teams…",
   "search.code_kind": "Search code…",
+  "search.code_empty": "Start a code search.",
+  "search.code_empty_description": "Enter a keyword to search across the code.",
   "search.code_search_unavailable": "Code search is currently not available. Please contact the site administrator.",
   "search.code_search_by_git_grep": "Current code search results are provided by \"git grep\". There might be better results if site administrator enables Repository Indexer.",
   "search.package_kind": "Search packages…",
@@ -1357,10 +1359,13 @@
   "repo.projects.desc": "Manage issues and pulls in projects.",
   "repo.projects.description": "Description (optional)",
   "repo.projects.description_placeholder": "Description",
+  "repo.projects.empty": "No projects yet.",
+  "repo.projects.empty_description": "Create a project to coordinate issues and pull requests.",
   "repo.projects.create": "Create Project",
   "repo.projects.title": "Title",
   "repo.projects.new": "New Project",
   "repo.projects.new_subheader": "Coordinate, track, and update your work in one place, so projects stay transparent and on schedule.",
+  "repo.projects.no_results": "No projects match your search.",
   "repo.projects.create_success": "The project \"%s\" has been created.",
   "repo.projects.deletion": "Delete Project",
   "repo.projects.deletion_desc": "Deleting a project removes it from all related issues. Continue?",
@@ -2722,6 +2727,8 @@
   "org.members": "Members",
   "org.teams": "Teams",
   "org.code": "Code",
+  "org.repos.empty": "No repositories yet.",
+  "org.repos.empty_description": "Create a repository to share code with the organization.",
   "org.lower_members": "members",
   "org.lower_repositories": "repositories",
   "org.create_new_team": "New Team",
@@ -2858,6 +2865,8 @@
   "org.worktime.date_range_end": "End date",
   "org.worktime.query": "Query",
   "org.worktime.time": "Time",
+  "org.worktime.empty": "No worktime data yet.",
+  "org.worktime.empty_description": "Adjust the date range to view tracked time.",
   "org.worktime.by_repositories": "By repositories",
   "org.worktime.by_milestones": "By milestones",
   "org.worktime.by_members": "By members",