[Feature]: Badge-with-X input for groups and users in role form

Parent PRD

#195

What to build

Replace the comma-separated text input for groups in the role form dialog with a badge-with-X-to-remove component. Add an identical input for users. Both principal types use the same shared input component pattern.

Key decisions from the PRD

• Shared badge-with-X input component for both groups and users
• Text input to type and add new entries (Enter or comma to confirm)
• X button on each badge to remove
• Groups and users sections in the General tab of the role form
• Form state, reset logic, and onSubmit parsing wired for both fields
• Admin role can have users assigned via email (no restriction)
• i18n keys for labels, placeholders, and help text

Acceptance criteria

• Groups input in role form uses badge-with-X pattern (replacing comma-separated text)
• Users input in role form uses the same badge-with-X pattern
• Typing an entry and pressing Enter/comma adds it as a badge
• Clicking X on a badge removes the entry
• Form correctly serializes both assigned_groups and assigned_users arrays on submit
• Form correctly populates badges when editing an existing role
• Admin role can have users assigned
• i18n translation keys added for user input labels/placeholders/help text (all locales)

Blocked by

• Blocked by #196
• Blocked by #198

User stories addressed

• User story 4 (add/remove users with badge-with-X)
• User story 5 (groups input also upgraded to badge-with-X)
• User story 6 (Admin role assignable via email)

Start with the role form dialog and inspect the shared badge-with-X input pattern, along with the work planned in blocked issues #196 and #198. Implement the groups and users fields, then verify add/remove behavior, edit-state population, submission arrays, Admin user assignment, and translation keys across locales.