feat: always show payment requests note ui #1358

Twin: synonymdev/bitkit-ios#817
Refs:

• fix: surface payment request details in sheet #1336
• fix: surface payment request details in sheet #1337

Problem or use case

A Payment Request without a note shows only the FROM cell on the confirmation sheet. The cell takes half the row, the divider under it stops halfway, and the space where FOR sits stays empty, so the sheet looks unfinished.

Proposed solution

• The FOR cell always shows. Without a note it reads "Not specified" in the secondary text colour, as @aldertnl proposed.
• The text comes from a new localized string.
• Android: in SendConfirmScreen.kt, the no-note branch renders FillWidth() in place of the FOR SendCell. It renders the SendCell with the "Not specified" text instead, keeping the PaymentRequestFor test tag.
• The details view behind Show details stays as it is.
• The request-summary.xml journey's no-note step changes from "For is not shown" to "For shows Not specified".

Done when:

• A request without a note shows FROM and FOR side by side, with FOR reading "Not specified".
• A request with a note shows its note in FOR, as today.
• The updated request-summary.xml journey passes.

Alternatives considered

• Make FROM full width when there is no note. The row stays tidy, but its shape changes from one request to the next.
• Have Paykit Server add a default note such as "Shop order 001234". It only helps requests from shops; a contact's request can still arrive without a note.

Additional context

• No Figma frame covers this state; the empty-state text was agreed with @aldertnl.