feat(dashboard): show admin hints and add the hints admin page

README.md

@@ -57,6 +57,9 @@ To Be Played is split into three repositories:
 - **Admin** (PLATFORM_ADMIN only, `/admin/users`): search the users, block, unblock and delete them (the email is
   typed to confirm a delete). "View as" in the menu switches the own session to User or Auditor and back; a badge
   shows the lower role. Auth checks every right on the server.
+- **Dashboard hints**: news from the admin at the bottom of the dashboard, one at a time. A "Dismiss" hint closes
+  after 30 s or with X and comes back in the next browser session unless "Do not show again" is ticked; an
+  "Accept" hint stays until "OK". Admins write, preview and end hints on `/admin/hints` (Auth stores them).
 - **Correct game data** (AUDITOR or higher): "Correct data" on the game detail page changes name, header image,
   speedrun link, moods, endless flag and genres for every user; each field goes back to the source on its own.
 - **Delete my account** in the settings: a dialog asks for the own email and the password. Auth blocks the