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/ToolsUpdate.css

@@ -1 +0,0 @@
-.aksrt-update__changelog[data-v-8fad1124]{margin-top:16px}.aksrt-update__changelog pre[data-v-8fad1124]{margin:8px 0 0;padding:12px 14px;border-radius:12px;background:#101828;color:#d0d7e2;font-size:12px;line-height:1.7;white-space:pre-wrap;word-break:break-word}.aksrt-update__grid[data-v-8fad1124]{display:grid;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));gap:12px}.aksrt-update__guide[data-v-8fad1124]{display:flex;flex-direction:column;gap:4px;padding:14px;border:1px solid #eef1f6;border-radius:12px;text-decoration:none;color:inherit;background:#fafafa}.aksrt-update__guide[data-v-8fad1124]:hover{border-color:#1890ff;background:#f5faff}.aksrt-update__guide span[data-v-8fad1124]{font-size:12px;color:#667085}