chore(admin): stop tracking SPA build; add native product meta box

Remove assets/admin/build from version control (local build only going
forward). Add AKSRT_Product_Meta_Box so product price/stock/shipping/after-
sale fields can be edited on the native aksrt_product edit screen without
the SPA product drawer.

assets/admin/build/ThemeInfoPage.css

@@ -1 +0,0 @@
-.aksrt-theme-info__loading[data-v-ded10315]{display:flex;justify-content:center;padding:60px 0}.aksrt-theme-info__card[data-v-ded10315]{margin-bottom:16px}.aksrt-theme-info__modules[data-v-ded10315]{display:flex;flex-wrap:wrap;gap:8px}.aksrt-theme-info__module-tag[data-v-ded10315]{display:inline-flex;align-items:center;gap:5px}.aksrt-theme-info__links[data-v-ded10315]{display:flex;flex-wrap:wrap;gap:12px}.aksrt-theme-info__link[data-v-ded10315]{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-ded10315]:hover{background:#e8eaed}