Wire role management tab to RBAC APIs

[jayvenn21]

Summary

• add a Role Management data layer for Custos RBAC role endpoints
• wire the admin Role Management tab to list roles, load privileges/member counts, create/update roles, and add/remove role privileges
• add MSW handlers and an e2e test for the role-management flow
• fix existing portal compile issues in the account menu/nav and Playwright auth fixture

Testing

• PATH=/opt/homebrew/opt/node@22/bin:$PATH corepack pnpm typecheck
• PATH=/opt/homebrew/opt/node@22/bin:$PATH corepack pnpm lint
• PATH=/opt/homebrew/opt/node@22/bin:$PATH corepack pnpm test
• PATH=/opt/homebrew/opt/node@22/bin:$PATH corepack pnpm exec playwright test tests/role-management.e2e.ts --timeout=60000
• go test ./...

Built on top of merged PR #520 and current master (#523/#521 included).

[lahirujayathilake]

@jayvenn21 thanks for the PR. I have added some review comments.

[jayvenn21]

@lahirujayathilake thanks for the feedback, i've made some changes with a new commit addressing the review. please take a look if there are any further changes to be made

[lahirujayathilake]

@jayvenn21 , I have added some comments and some need clarifications. Can you check those?

[jayvenn21]

@lahirujayathilake I've addressed all the feedback in the latest commit, please let me know if there are any further changes to be made

[lahirujayathilake]

@jayvenn21 LGTM 👍🏼