Add confirmation dialogs for destructive actions

[hasnaintypes]

Context

Destructive actions (deleting accounts, transactions, revoking sessions) happen immediately with no confirmation. Users can accidentally lose data.

What needs to be done

Add a confirmation dialog before:

• Deleting a transaction
• Deleting a bank account
• Bulk deleting transactions
• Revoking a session

Implementation hints

• Use shadcn/ui AlertDialog component (already available at src/components/ui/alert-dialog.tsx)
• Create a reusable ConfirmDialog wrapper with props: title, description, onConfirm, variant (destructive/default)
• Wire it into existing delete buttons

Acceptance criteria

• Reusable confirm dialog component
• Transaction delete uses it
• Account delete uses it
• Passes pnpm check