Implement Admin user management UI

[fusion94]

Description

Build the admin-only UI for managing user accounts in the application.

Features

Users Page (/settings/users) — Admin Only

• Table of all user accounts: email, display name, role, created date
• Role badges (Admin / Member)
• Action buttons: edit, delete
• "Create User" button

Create User Dialog

• Form fields: email, display name, password, confirm password, role (dropdown)
• Password strength indicator (min 12 characters)
• Zod validation from shared schemas
• Success notification on creation
• Copy temporary password option

Edit User Dialog

• Pre-populated form with current user data
• Optional password reset field (leave blank to keep current)
• Role dropdown (cannot demote last admin — show disabled/warning)
• Display name and email editable

Delete User Dialog

• Confirmation with user's name/email
• Warning about data ownership (bottles/notes added by this user)
• Blocked for the last admin account
• Blocked for self-deletion (cannot delete yourself)

Navigation

• "Users" menu item visible only to admin users
• Settings section with user management tab

Acceptance Criteria

• Users page only accessible by admin users
• User list displays all accounts
• Create user form validates and submits
• Edit user form pre-populates and updates
• Delete requires confirmation
• Last admin cannot be deleted or demoted
• Role changes take effect immediately
• Non-admin users don't see the Users menu item

References

• PRD Section 3: US-13 (User Stories)
• PRD Section 4: FR-7 (User Management)