feat(frontend): add Helm chart browser, monitoring, chart-references and values templates pages

Add new frontend pages for the multi-tenant OCDP platform:

- Charts page (/charts): Browse Harbor OCI registries to list Helm chart repositories
  and versions, with deploy modal to launch charts on selected clusters
- Monitoring page (/monitoring): Display cluster metrics (CPU/Memory/GPU usage)
  and per-node details with resource utilization bars
- Chart References page (/chart-references): CRUD for chart metadata references
- Values Templates page (/templates): CRUD for Helm values templates with version
  history and rollback support
- Sidebar: Add Charts navigation, update Storage and Templates links
- api.ts: Add all API client functions (clusterApi, registryApi, instanceApi,
  monitoringApi, storageApi, chartReferenceApi, valuesTemplateApi,
  workspaceApi, userApi) with full TypeScript types

Note: deploy flow and values template rollback not yet end-to-end tested.

frontend/.gitignore

@@ -1,27 +1,41 @@
-# Logs
-logs
-*.log
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+/node_modules
+/.pnp
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/versions
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
 npm-debug.log*
 yarn-debug.log*
 yarn-error.log*
-pnpm-debug.log*
-lerna-debug.log*
+.pnpm-debug.log*
 
-node_modules
-dist
-dist-ssr
-*.local
+# env files (can opt-in for committing if needed)
+.env*
 
-# Editor directories and files
-.vscode/*
-!.vscode/extensions.json
-.idea
-.DS_Store
-*.suo
-*.ntvs*
-*.njsproj
-*.sln
-*.sw?
-src/api/generated
-src/api/generated-new
-src/api/generated-test
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts