docs: add a privacy policy for the mobile app

Claude-Session: https://claude.ai/code/session_01BDVpJ78s7RQVcj57vjTcfA

PRIVACY.md

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+# Privacy Policy
+
+_Last updated: 2026-09-29_
+
+This policy covers tty7 and the tty7 mobile app ("the app").
+
+## Summary
+
+tty7 does not collect, sell or share personal data. There are no accounts, no
+analytics, no advertising and no tracking. Your terminal data travels only
+between your phone and a computer you paired it with yourself.
+
+## What the app handles
+
+- **Terminal content and input.** The app shows the terminal panes and agent
+  status of your paired computer and sends your keystrokes back to it. This data
+  goes directly between your devices and is not stored by us.
+- **Pairing information.** To connect, the app keeps a device key and the list
+  of computers you paired with on your phone. Your computer keeps the list of
+  phones it trusts. Both stay on your devices. You can unpair a phone from the
+  desktop app at any time (Settings → Mobile).
+- **Camera.** The camera is used only to scan the pairing QR code shown on your
+  computer. Images are processed on the phone and never stored or sent anywhere.
+- **Local network.** The app may look for your computer on the local network to
+  connect to it directly.
+
+## How connections work
+
+The phone connects to your computer with [iroh](https://iroh.computer).
+Connections are end-to-end encrypted. When a direct connection is not possible,
+traffic passes through a public relay server, which forwards encrypted packets it
+cannot read. Relay operators may see technical connection metadata such as IP
+addresses, as with any internet service.
+
+## Third parties
+
+The app contains no third-party analytics, crash reporting or advertising SDKs.
+
+## Children
+
+The app is not directed at children and collects no data from anyone.
+
+## Changes
+
+Changes to this policy are published in this file; its history is visible in
+the repository.
+
+## Contact
+
+Questions: open an issue at <https://github.com/l0ng-ai/tty7/issues>.