feat: add visible build commit hash footer to dashboard layout

The build hash was only in the sidebar which could be hidden or cut off.
Added a proper footer to the main content area so the commit hash is
always visible at the bottom of every dashboard page.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/app/(dashboard)/layout.tsx

@@ -22,6 +22,9 @@ export default async function DashboardLayout({
         <main className="flex-1 p-8 overflow-auto">
           {children}
         </main>
+        <footer className="px-8 py-3 text-xs text-gray-400 border-t border-gray-200">
+          Build {process.env.NEXT_PUBLIC_BUILD_HASH || 'dev'}
+        </footer>
       </div>
     </div>
   );