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/SchemaPage.css

@@ -1 +0,0 @@
-.aksrt-schema-page[data-v-a4bec770]{max-width:1100px;margin:0 auto}.aksrt-schema-page__tool-actions[data-v-a4bec770]{display:flex;justify-content:flex-end;margin-top:16px}.aksrt-schema-page__field-hint[data-v-a4bec770]{margin:8px 0 0;font-size:12px;color:#8a909c}.captcha-test-overlay[data-v-a4bec770]{position:fixed;top:0;left:0;width:100%;height:100%;background:#00000080;display:flex;justify-content:center;align-items:center;z-index:9999}.captcha-test-panel[data-v-a4bec770]{background:#fff;border-radius:12px;width:420px;max-width:90%;box-shadow:0 8px 32px #0000002e}.captcha-test-header[data-v-a4bec770]{display:flex;justify-content:space-between;align-items:center;padding:18px 22px;border-bottom:1px solid #e8e8ec;font-size:16px;font-weight:600}.captcha-test-close[data-v-a4bec770]{background:none;border:none;font-size:24px;cursor:pointer;color:#999;padding:0;line-height:1}.captcha-test-close[data-v-a4bec770]:hover{color:#333}.captcha-test-body[data-v-a4bec770]{padding:24px;min-height:180px;display:flex;justify-content:center;align-items:center}