Move iOS app into repo with public-only Convex sync and proprietary licensing

[lawrencecchen]

Summary

• Move the iOS app from ~/fun/cmux/ios-app into this repo as ios/ without moving the existing macOS app layout.
• Add iOS-side sync helpers to keep Convex ownership in ~/fun/cmux while importing only public config:
  • ios/scripts/sync-public-convex-vars.sh (whitelisted public env keys only)
  • ios/scripts/sync-convex-types.sh (regenerate ConvexApiTypes.swift from ~/fun/cmux/packages/convex)
• Keep ios/Sources/Config/LocalConfig.plist gitignored and update Environment.swift + LocalConfig.example.plist for explicit dev/prod public overrides.
• Add explicit license scoping so ios/** is proprietary (ios/LICENSE) and document the repo-wide scope in LICENSE_SCOPE.md.

Testing

• cd ios && ./scripts/sync-public-convex-vars.sh --source-root /Users/lawrencechen/fun/cmux (pass)
• cd ios && ./scripts/sync-convex-types.sh --source-root /Users/lawrencechen/fun/cmux (pass)
• cd ios && xcodegen generate (pass)
• cd ios && xcodebuild -project cmux.xcodeproj -list (pass)
• cd . && bash -n ios/scripts/sync-public-convex-vars.sh ios/scripts/sync-convex-types.sh ios/scripts/reload.sh ios/scripts/device.sh ios/scripts/testflight.sh (pass)
• Secret-safety verification on staged diff for known private key/token patterns (no matches)

Issues

• Task reference: HQ request on 2026-02-23 to migrate iOS app into this repo, keep Convex source in ~/fun/cmux, and ensure no non-public secrets are committed.