Remove unused @rspack/core devDependency

[blaipr]

Summary

• @rspack/core is not imported or referenced anywhere in the codebase
• Only installed to satisfy optional peerDependencies of loaders (babel-loader, css-loader, postcss-loader, sass-loader, html-webpack-plugin) that support both webpack and rspack
• The project uses webpack exclusively
• Removes ~60 transitive packages from the lock file

Test plan

• npm install succeeds without errors
• npm test passes
• npm run build succeeds

[cigamit]

After merging this, builds are now failing.

INLINE_RUNTIME_CHUNK=false node scripts/build.js",
"node:internal/modules/esm/resolve:1001",
"    throw error;",
"    ^",
"Error [ERR_MODULE_NOT_FOUND]: Cannot find package '@rspack/core' imported from /tmp/src/awx/ui/node_modules/inject-manifest-plugin/dist/index.js",
"    at Object.getPackageJSONURL (node:internal/modules/package_json_reader:314:9)",
"    at packageResolve (node:internal/modules/esm/resolve:768:81)",
"    at moduleResolve (node:internal/modules/esm/resolve:855:18)",
"    at defaultResolve (node:internal/modules/esm/resolve:985:11)",
"    at #cachedDefaultResolve (node:internal/modules/esm/loader:731:20)",
"    at #resolveAndMaybeBlockOnLoaderThread (node:internal/modules/esm/loader:767:38)",
"    at ModuleLoader.resolveSync (node:internal/modules/esm/loader:790:52)",
"    at #cachedResolveSync (node:internal/modules/esm/loader:750:25)",
"    at ModuleLoader.getModuleJobForRequire (node:internal/modules/esm/loader:459:50)",
"    at new ModuleJobSync (node:internal/modules/esm/module_job:392:34) {",
"  code: 'ERR_MODULE_NOT_FOUND'",
"}",
"",
"Node.js v22.22.2",
"make: *** [Makefile:394: awx/ui/.ui-built] Error 1",
"ERROR: process \"/bin/sh -c make sdist && /var/lib/awx/venv/awx/bin/pip install dist/awx.tar.gz\" did not complete successfully: exit code: 2"

[blaipr]

inject-manifest-plugin@0.6.5 lists @rspack/core as a peer dependency and unconditionally imports it at runtime in dist/index.js, so removing it breaks the production build. The fix is to add @rspack/core back as a devDependency. I will open a PR to restore it.