Enhanced Timing App Support for Fixed-Time Events with Multiple Checkpoints

The current fixed-time configuration in the UltraSignup timing app only supports a single checkpoint per loop, which limits its usefulness for more complex events.

Use Case:
Some fixed-time races (e.g., 12/24/48 hour events) use a looped course with multiple timing points, such as:

Runners start at Checkpoint A,

Run X miles to Checkpoint B,

Turn around and return to Checkpoint A—completing one loop.

Feature Request:

Enable multiple checkpoints per loop within fixed-time race configuration

Allow timing data to be collected and synced from both Checkpoint A and B

Maintain support for looped logic while accurately tracking bidirectional timing data across all race durations

Adding this feature would provide better support for a growing segment of loop-based endurance events and improve timing accuracy for both RDs and participants.