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/ajv/lib/dot/multipleOf.jst

@@ -0,0 +1,22 @@
+{{# def.definitions }}
+{{# def.errors }}
+{{# def.setupKeyword }}
+{{# def.$data }}
+
+{{# def.numberKeyword }}
+
+var division{{=$lvl}};
+if ({{?$isData}}
+      {{=$schemaValue}} !== undefined && (
+      typeof {{=$schemaValue}} != 'number' ||
+    {{?}}
+      (division{{=$lvl}} = {{=$data}} / {{=$schemaValue}},
+      {{? it.opts.multipleOfPrecision }}
+        Math.abs(Math.round(division{{=$lvl}}) - division{{=$lvl}}) > 1e-{{=it.opts.multipleOfPrecision}}
+      {{??}}
+        division{{=$lvl}} !== parseInt(division{{=$lvl}})
+      {{?}}
+      )
+    {{?$isData}}  )  {{?}} ) {
+  {{# def.error:'multipleOf' }}
+} {{? $breakOnError }} else { {{?}}