fix(a11y): focus lost after declining planned-purchase cancel; Key Created dialog lacks role=dialog #1666

Discovered while verifying #1598 (burndown run 2026-11-04).

Summary

Two small dialog accessibility gaps on main:

1. Declining the "Cancel this scheduled purchase" confirm (Plans, planned purchase row X) leaves focus on <body> instead of the opener: after the decline plans.ts (disable case, ~lines 585-600) calls loadPlannedPurchases(), which re-renders the row and removes the opener element.
2. The one-time "Key Created Successfully" dialog (data-require-ack) has no role="dialog" (and so no accessible dialog semantics).

Steps to reproduce

1. Plans > a planned purchase row > X > close the confirm with Esc or its X: document.activeElement is BODY.
2. Create an API key; inspect the Key Created dialog: no role attribute.

Expected behaviour

1. Focus returns to the re-rendered row's control (or the planned-purchases heading) after the list reloads.
2. The dialog has role="dialog" (or alertdialog), aria-modal="true" and a label.

Proposed fix

1. After loadPlannedPurchases() resolves, focus the matching row's control by id, falling back to the section heading.
2. Add the role/aria attributes in the Key Created markup.

References

• Found verifying ui(dialogs): one dialog chrome with a header close button #1598 (both pre-existing on main). Severity: low.