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/ThemeInfoPage.css

@@ -0,0 +1 @@
+.aksrt-theme-info__loading[data-v-4017c910]{display:flex;justify-content:center;padding:60px 0}.aksrt-theme-info__card[data-v-4017c910]{margin-bottom:16px}.aksrt-theme-info__modules[data-v-4017c910]{display:flex;flex-wrap:wrap;gap:8px}.aksrt-theme-info__module-tag[data-v-4017c910]{display:inline-flex;align-items:center;gap:5px}.aksrt-theme-info__links[data-v-4017c910]{display:flex;flex-wrap:wrap;gap:12px}.aksrt-theme-info__link[data-v-4017c910]{display:inline-flex;align-items:center;gap:6px;padding:8px 16px;border-radius:6px;background:#f5f7fa;color:#333;text-decoration:none;font-size:13px;transition:background .2s}.aksrt-theme-info__link[data-v-4017c910]:hover{background:#e8eaed}