refactor(pairing): one way in on each side instead of three

[arzafran]

What this does

Pairing a phone offered three entry points and two buttons for a single action, and the two devices did not agree on what pairing looked like.

The phone screen had a QR scanner, a combined-code field with a "Use This Code" button, and an Advanced section holding separate ticket and token fields behind its own "Connect" button. Two buttons that both connect, one of which only worked with the fields nobody was meant to use. The file's own doc comment described those fields as legacy.

The Mac had the QR, the combined code shown as selectable text with a Copy button, and directly below that a "Can't scan? Paste the payload and token manually" disclosure showing the same secret split into two labelled boxes. The question it asked was already answered by the copyable code sitting above it.

Both legacy paths are gone. The Mac shows the QR and the one code the QR encodes. The phone scans or pastes that code, and its single button now says Connect.

Summary

• Sources/SettingsView.swift: removed the manual-fallback DisclosureGroup; the pairing subtitle no longer promises payload-and-token entry
• ios/.../PairConnectView.swift: removed the Advanced section and the duplicate Connect button; the remaining button picks up the isConnecting guard the removed one owned
• pairingTicketDraft / pairingTokenDraft stay on AppStore — applyPairingCode still fills them and connectManually still reads them, they are simply no longer bound to text fields
• Nine localization keys dropped across the two catalogs; pairing.connect.useCodeButton retranslated for its new label

Why this is safe to remove rather than keep as a fallback

The fallback existed for "cannot scan, or the combined paste did not parse". The Mac renders the exact string the QR encodes, selectable, with a Copy button. Pasting that is the fallback. The split fields only ever offered a second way to transfer the same two values, which is what made the screen confusing.

Test plan

• xcodebuild -scheme programa builds
• xcodebuild -scheme ProgramaSpike builds for iOS Simulator
• Mac: Settings ▸ Phone ▸ Pair a Device — QR renders, code is selectable, Copy works, countdown still ticks
• Phone: scan the QR, and separately paste the copied code and press Connect

Note

Stacked on #232 and based on that branch so this shows one commit, and so both ship in a single release.