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/@wordpress/components/build/external-link/styles/external-link-styles.js

@@ -0,0 +1,26 @@
+"use strict";
+
+var _interopRequireDefault = require("@babel/runtime/helpers/interopRequireDefault");
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.StyledIcon = void 0;
+var _base = _interopRequireDefault(require("@emotion/styled/base"));
+var _icons = require("@wordpress/icons");
+function _EMOTION_STRINGIFIED_CSS_ERROR__() { return "You have tried to stringify object returned from `css` function. It isn't supposed to be used directly (e.g. as value of the `className` prop), but rather handed to emotion so it can handle it (e.g. as value of `css` prop)."; }
+const StyledIcon = ( /*#__PURE__*/0, _base.default)(_icons.Icon, process.env.NODE_ENV === "production" ? {
+  target: "esh4a730"
+} : {
+  target: "esh4a730",
+  label: "StyledIcon"
+})(process.env.NODE_ENV === "production" ? {
+  name: "rvs7bx",
+  styles: "width:1em;height:1em;margin:0;vertical-align:middle;fill:currentColor"
+} : {
+  name: "rvs7bx",
+  styles: "width:1em;height:1em;margin:0;vertical-align:middle;fill:currentColor",
+  map: "/*# sourceMappingURL=data:application/json;charset=utf-8;base64,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 */",
+  toString: _EMOTION_STRINGIFIED_CSS_ERROR__
+});
+exports.StyledIcon = StyledIcon;
+//# sourceMappingURL=external-link-styles.js.map

node_modules/@wordpress/components/build/external-link/styles/external-link-styles.js.map

@@ -0,0 +1 @@
+{"version":3,"names":["_icons","require","_EMOTION_STRINGIFIED_CSS_ERROR__","StyledIcon","_base","default","Icon","process","env","NODE_ENV","target","label","name","styles","map","toString","exports"],"sources":["@wordpress/components/src/external-link/styles/external-link-styles.ts"],"sourcesContent":["/**\n * External dependencies\n */\nimport styled from '@emotion/styled';\n\n/**\n * WordPress dependencies\n */\nimport { Icon } from '@wordpress/icons';\n\nexport const StyledIcon = styled( Icon )`\n\twidth: 1em;\n\theight: 1em;\n\tmargin: 0;\n\tvertical-align: middle;\n\tfill: currentColor;\n`;\n"],"mappings":";;;;;;;;AAQA,IAAAA,MAAA,GAAAC,OAAA;AAAwC,SAAAC,iCAAA;AAEjC,MAAMC,UAAU,GAAG,kBAAAC,KAAA,CAAAC,OAAA,EAAQC,WAAI,EAAAC,OAAA,CAAAC,GAAA,CAAAC,QAAA;EAAAC,MAAA;AAAA;EAAAA,MAAA;EAAAC,KAAA;AAAA,CAAC,CAAC,CAAAJ,OAAA,CAAAC,GAAA,CAAAC,QAAA;EAAAG,IAAA;EAAAC,MAAA;AAAA;EAAAD,IAAA;EAAAC,MAAA;EAAAC,GAAA;EAAAC,QAAA,EAAAb;AAAA,EAMvC;AAACc,OAAA,CAAAb,UAAA,GAAAA,UAAA"}