Add a Remote scroll-to-top button

[enaboapps]

Closes #107

Summary

• add an opt-in 48-point floating Scroll to top control to sticky Screen layouts
• enable it for all four connected Remote surfaces while leaving disconnected, recovering, and unavailable states unchanged
• respect Reduce Motion, prevent duplicate activations, cancel touch or drag interruptions, and preserve controls-only scanning
• add bottom clearance plus accessibility and physical smoke-test criteria

Validation

• npm run validate — passed (49 suites, 362 tests, Expo Doctor 21/21)
• npx expo config --type public — inspected; version/build, native identifiers, permissions, and configuration remain unchanged
• CI validate — passed
• CI clean Android prebuild and assembleDebug — passed
• CI clean iOS prebuild, CocoaPods install, and simulator build — passed
• independent latest-head review of a5e7bdd — no findings; the initial touch-interruption finding was resolved and re-reviewed
• Android OPD2403 development client — Metro bundled the final source successfully, but the already-installed client remained stuck on its native Reloading... overlay; visual, TalkBack, and Switch Access checks remain pending
• iOS physical checks — pending because no iOS device/build environment is attached to this Windows workspace

Compatibility

• no BLE, protocol, command, storage, navigation, native configuration, dependency, or version changes
• existing untracked capture and attachment directories were preserved