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/v8-to-istanbul/index.d.ts

@@ -0,0 +1,25 @@
+/// <reference types="node" />
+
+import { Profiler } from 'inspector'
+import { CoverageMapData } from 'istanbul-lib-coverage'
+import { SourceMapInput } from '@jridgewell/trace-mapping'
+
+declare type Sources =
+  | {
+      source: string
+    }
+  | {
+      source: string
+      originalSource: string
+      sourceMap: { sourcemap: SourceMapInput }
+    }
+declare class V8ToIstanbul {
+  load(): Promise<void>
+  destroy(): void
+  applyCoverage(blocks: ReadonlyArray<Profiler.FunctionCoverage>): void
+  toIstanbul(): CoverageMapData
+}
+
+declare function v8ToIstanbul(scriptPath: string, wrapperLength?: number, sources?: Sources, excludePath?: (path: string) => boolean): V8ToIstanbul
+
+export = v8ToIstanbul