fix: prevent asset conflicts between React and Grid.js versions

Add coexistence checks to all enqueue methods to prevent loading
both React and Grid.js assets simultaneously.

Changes:
- ReactAdmin.php: Only enqueue React assets when ?react=1
- Init.php: Skip Grid.js when React active on admin pages
- Form.php, Coupon.php, Access.php: Restore classic assets when ?react=0
- Customer.php, Product.php, License.php: Add coexistence checks

Now the toggle between Classic and React versions works correctly.

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

node_modules/markdown-it/lib/rules_inline/html_inline.js

@@ -0,0 +1,47 @@
+// Process html tags
+
+'use strict';
+
+
+var HTML_TAG_RE = require('../common/html_re').HTML_TAG_RE;
+
+
+function isLetter(ch) {
+  /*eslint no-bitwise:0*/
+  var lc = ch | 0x20; // to lower case
+  return (lc >= 0x61/* a */) && (lc <= 0x7a/* z */);
+}
+
+
+module.exports = function html_inline(state, silent) {
+  var ch, match, max, token,
+      pos = state.pos;
+
+  if (!state.md.options.html) { return false; }
+
+  // Check start
+  max = state.posMax;
+  if (state.src.charCodeAt(pos) !== 0x3C/* < */ ||
+      pos + 2 >= max) {
+    return false;
+  }
+
+  // Quick fail on second char
+  ch = state.src.charCodeAt(pos + 1);
+  if (ch !== 0x21/* ! */ &&
+      ch !== 0x3F/* ? */ &&
+      ch !== 0x2F/* / */ &&
+      !isLetter(ch)) {
+    return false;
+  }
+
+  match = state.src.slice(pos).match(HTML_TAG_RE);
+  if (!match) { return false; }
+
+  if (!silent) {
+    token         = state.push('html_inline', '', 0);
+    token.content = state.src.slice(pos, pos + match[0].length);
+  }
+  state.pos += match[0].length;
+  return true;
+};