Finish Comments/Edit page (UpdateComment)

[adedw]

What to build

The Comments/Edit page is a stub with a TODO. Implement an UpdateComment command in Application and wire the page via direct ICommandHandler injection (the backlog's IMessageHandler wording predates the mediator removal). A user can edit their own comment; the change persists and renders on the map/list.

Acceptance criteria

• User opens Edit for their comment, changes the text, saves — the change persists and is visible on the map/list.
• Ownership enforced: another user's comment is not editable.
• Handler follows current conventions: record UpdateCommentCommand : ICommand[<TResult>] + sealed handler with constructor DI, page model injects ICommandHandler<UpdateCommentCommand, ...> directly.

Blocked by

None (can start immediately).