Re-enable RouterApp components for integration tests

The RouterApp components were temporarily disabled, causing integration
tests to fail. Re-enabled them and updated knip config accordingly.

Changes:
- Renamed RouterApp.*.jsx.skip back to RouterApp.*.jsx
- Removed RouterApp-related ignores from knip.ts
- Removed react-router-dom from ignoreDependencies

The RouterApp.server.jsx already has the correct import for
react-router-dom v6 (react-router-dom/server.js).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

knip.ts

@@ -112,12 +112,6 @@ const config: KnipConfig = {
         '**/app-react16/**/*',
         // Playwright support files and helpers - generated by cypress-on-rails gem
         'e2e/playwright/support/**',
-        // Temporarily disabled RouterApp components due to react-router-dom version mismatch
-        'client/app/components/RouterFirstPage.jsx',
-        'client/app/components/RouterLayout.jsx',
-        'client/app/components/RouterSecondPage.jsx',
-        'client/app/routes/routes.jsx',
-        'client/app/startup/RouterApp.*.jsx.skip',
       ],
       project: ['**/*.{js,cjs,mjs,jsx,ts,cts,mts,tsx}!', 'config/webpack/*.js'],
       paths: {
@@ -154,8 +148,6 @@ const config: KnipConfig = {
         'url-loader',
         // Transitive dependency of shakapacker but listed as direct dependency
         'webpack-merge',
-        // Temporarily disabled due to version mismatch (v5 installed but v6 expected)
-        'react-router-dom',
       ],
     },
   },