feat(admin): bump react-router and adapt new routes package (#11887)

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **New Features**
  - Added new admin routes: "auth", "setup", and "notFound" for improved navigation and access within the admin interface.
  - Introduced a utility for simplified and flexible lazy loading of React components with fallback support.

- **Improvements**
  - Updated routing structure in the admin frontend for clearer route management and enhanced Sentry integration.
  - Centralized route definitions for easier maintenance and consistency.
  - Upgraded dependencies to support the latest React Router and React versions.
  - Enhanced asynchronous handling in setup form navigation.

- **Chores**
  - Updated project references and workspace dependencies for better package management.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/routes/package.json

@@ -4,7 +4,7 @@
   "private": true,
   "type": "module",
   "exports": {
-    ".": "./src/routes.ts"
+    ".": "./src/index.ts"
   },
   "scripts": {
     "build": "r build.ts"
@@ -16,7 +16,8 @@
     "query-string": "^9.1.1",
     "vitest": "^3.0.6"
   },
-  "optionalDependencies": {
-    "react-router-dom": "^6.28.0"
+  "peerDependencies": {
+    "react": "^19.1.0",
+    "react-router-dom": "^7.5.1"
   }
 }