feat: add PTP integration tests for LTC timecode synchronization

This commit adds comprehensive test coverage for the PTP and LTC timecode synchronization logic, including:

- PTP client initialization tests
- PTP disabled state handling
- LTC to PTP time conversion
- Frame timing precision
- Offset tracking and jitter calculation
- Interface change handling

The tests validate key aspects of the synchronization process, ensuring accurate timecode conversion, offset tracking, and client behavior under different configurations.

Co-authored-by: aider (openrouter/anthropic/claude-sonnet-4) <aider@aider.chat>

src/lib.rs

@@ -0,0 +1,7 @@
+//! Timeturner library for LTC and PTP synchronization
+
+pub mod config;
+pub mod ptp;
+pub mod serial_input;
+pub mod sync_logic;
+pub mod ui;