Support rotated display and gesture orientation

[PurpleSentinel]

Parent: #23

Summary

Allow the device to be mounted at 0, 90, 180, or 270 degrees while keeping text and directional gestures intuitive.

Acceptance criteria

• Persist the selected rotation.
• Rotate both rendering and gesture direction mapping consistently.
• Keep circular-layout fit guarantees at every orientation.
• Show a safe preview before saving.
• Add mapping and layout tests for all four rotations.

Roadmap group

Driver display and alerts