chore: keep each screen's figma frames in the screen file

[ovitrif]

Problem or use case

iOS has no mapping from a view to its Figma frame. AGENTS.md only says to start from the latest Bitkit - Handoff vNN page, so each PR author and reviewer searches Figma by hand. That breaks down when a spec arrives later on another page: the Payment Request confirmation for #791 was specced on Bitkit - Refactor v63, and a review compared the PR against the superseded Handoff v62 frames. SendConfirmationView.swift also renders several designs (on-chain and Lightning send, subscription and payment request states), and nothing records which frame belongs to which.

Proposed solution

Adopt the same tag format as Android, as /// doc comment lines on each view that renders a whole Figma frame: every navigation destination (the views behind route enums such as SendRoute) and every sheet root.

/// Figma: Send (Paste) (On-chain) › Confirm Send Onchain
/// Figma (payment request): Bitkit - Refactor v63 › Send (Pay Payment Request) › Payment Request
/// Figma (payment request details): Bitkit - Refactor v63 › Send (Pay Payment Request) › Confirm Details
struct SendConfirmationView: View {

• Figma: <Section> › <Frame> is a frame on the latest Bitkit - Handoff vNN page.
• Figma: <Page> › <Section> › <Frame> is a frame on another page, for a spec that arrived later.
• Figma (<state>): … gives the frame for one state when a view renders several designs, one line per state.
• Figma: todo when the view shipped ahead of its design, Figma: n/a when no design is intended.
• One live frame per state. When a newer spec lands, its line replaces the old one.

The work, in one PR that changes only this concern:

1. Tag every navigation destination and sheet root view.
2. Add the two payment request states to SendConfirmationView.swift.
3. Add a check (unit test or build-phase script) that fails when a navigation destination or sheet root has no tag, or a tag doesn't match the grammar.
4. Point AGENTS.md and the PR template at the tags, with git grep -n "Figma:" -- 'Bitkit/Views' for an overview.

Acceptance

• Every navigation destination and sheet root view carries at least one valid Figma tag.
• SendConfirmationView.swift names the Refactor v63 Payment Request and Confirm Details frames for its payment request states.
• The check fails for an untagged navigation destination or sheet root.
• AGENTS.md and the PR template resolve a view's design through its tags.
• The PR changes only tags, the check and those instructions, with no UI or behaviour change.

Alternatives considered

• A central map like Android's docs/screens-map.md: the file every screen PR edits, which is what the Android twin removes.
• Tagging every View type: most are components inside a frame, so the tags would be noise.

Additional context

• The review that compared against Handoff v62: fix: surface payment request details in sheet #791 (review)
• Pair: chore: keep each screen's figma frames in the screen file bitkit-android#1346 (Android).