build(admin): track the SPA build output so git deploys carry it

assets/admin/build was gitignored, so servers deployed by git pull kept
running a stale admin bundle — the icon picker integration in the tabbar
and floating-button settings pages never reached them. Track the build
directory (rebuild with: cd assets/admin && npm run build) and commit the
current bundle containing the universal icon picker.

assets/admin/build/ToolsImportExport.css

@@ -0,0 +1 @@
+.aksrt-tools-output[data-v-c6830358]{margin:0;padding:14px;border-radius:12px;background:#101828;color:#d0d7e2;font-size:12px;line-height:1.7;white-space:pre-wrap;word-break:break-word}.aksrt-tools-hint[data-v-c6830358]{margin:12px 0 0;color:#667085;font-size:12px;line-height:1.7}