feat: add contact payment UI

[ben-kaufman]

Description

Adds the contact-payment UI that was intentionally left out of the private Paykit PR:

• Send -> Contact selection with contact-aware send headers.
• Contact avatars in the main activity lists, while contact-specific activity lists keep the standard arrow icon.
• Activity detail contact assignment, assigned-contact display, and detach action.
• Settings -> General -> Payment Preference toggles for Lightning/on-chain payment methods and private/public contact-payment publishing.

This targets codex/paykit-private-payments so it can be reviewed separately from the private Paykit core work.

Linked Issues/Tasks

Refs #539

Screenshot / Video

Not attached in this PR body. The UI was validated locally against the simulator flow, and this branch is intentionally scoped to UI/wiring on top of the private payments branch.

Verification

• swiftformat --lint Bitkit/Services/PrivatePaykitService+Endpoints.swift Bitkit/ViewModels/SettingsViewModel.swift Bitkit/Views/Settings/General/PaymentPreferenceView.swift Bitkit/Views/Wallets/Activity/ActivityRow.swift Bitkit/Views/Wallets/Activity/ActivityItemView.swift Bitkit/Views/Wallets/Send/SendContactSelectView.swift Bitkit/Views/Wallets/Send/SendOptionsView.swift Bitkit/Views/Wallets/Send/SendSheet.swift Bitkit/Views/Wallets/Activity/AssignActivityContactView.swift Bitkit/Components/PubkyContactAvatar.swift Bitkit/Components/PubkyContactRow.swift
• git diff --check
• git diff --cached --check
• node scripts/validate-translations.js
• env DEVELOPER_DIR=/Users/benk10/Downloads/Old\ Mac\ Backup/Xcode.app/Contents/Developer xcodebuild -quiet -project Bitkit.xcodeproj -scheme Bitkit -configuration Debug -destination id=15FE6795-02FB-4073-A427-63F0B39A3A17 -derivedDataPath /private/tmp/bitkit-contact-ui-build build

[chatgpt-codex-connector]

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[ben-kaufman]

About 2, I guess this is mostly a design / UI choice.
About 3, I assume this is the intention with it no? Ie. it's meant for when we can't know which contact the payment belongs to, so user can manually assign it.

[piotr-iohk]

About 2, I guess this is mostly a design / UI choice.

Added comment in figma.

[piotr-iohk]

LGTM. Re-tested failed scenarios - now pass.
Also no issue observed in e2e tests after paykit update.