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/PermissionsCapabilities.css

@@ -1 +0,0 @@
-.aksrt-cap-matrix__header[data-v-34bd6923]{display:flex;align-items:center;justify-content:space-between}.aksrt-cap-matrix__title[data-v-34bd6923]{margin:0;font-size:15px;font-weight:600}.aksrt-cap-matrix__desc[data-v-34bd6923]{margin:4px 0 0;font-size:12px;color:#8a909c}.aksrt-cap-matrix__cap[data-v-34bd6923]{display:flex;flex-direction:column;gap:4px}.aksrt-cap-matrix__cap code[data-v-34bd6923]{font-size:11px;color:#667085}.aksrt-cap-matrix__empty[data-v-34bd6923]{color:#c0c4cc}.aksrt-form-actions[data-v-34bd6923]{display:flex;justify-content:flex-end;margin-top:16px}