Align Account password dialog with form modals

[Kevinjohn]

Fixes #1236.

Changes

• Use the shared form dialog shell on Account, matching Add activity and Add resource.
• Put each password field in its own label/control row, with Cancel and Change password in the standard footer.
• Remove the redundant dialog description while preserving validation, success feedback, password clearing, and session revocation.
• Extend the password-auth browser flow to check the dialog layout, focus, footer, and Cancel action.

Merge predecessor: none.

Screenshots

Desktop:

Narrow viewport:

Validation

• pnpm run format:check
• pnpm run typecheck
• pnpm run lint
• pnpm run gate:all
• pnpm run e2e