Use accumulated TRIMP for FIT training effect

[cagnulein]

Summary

This changes the FIT aerobic total_training_effect estimate to prefer the accumulated TRIMP load that qfit already calculates, instead of using only a duration-normalized HR zone average.

Why

The previous zone-average formula made steady aerobic workouts look too low because the value barely increased with workout duration. Garmin describes Training Effect as accumulating during an activity, so using the already accumulated TRIMP value gives a more Garmin-like progression while keeping the existing zone-average fallback.

For the analyzed 30-minute indoor cycling sample, the current code produced about 0.8; the TRIMP-based mapping produces about 1.88, which is a more plausible minor/near-maintaining aerobic effect for a steady Z2 session.

Validation

• Ran git diff --check
• Recomputed the sample workout estimate from the attached FIT/log data: TRIMP 42.5388 maps to aerobic TE 1.883

No full build was run for this one-line calculation change.