Replace all instances of `detail=str(e)`, `detail=f"...{exc}"`, and similar
patterns that exposed internal exception messages to HTTP clients in
services/ml/app/main.py. All exception details are now logged server-side
only via logger.error(), while clients receive a generic "Internal server error"
message. Fixes 9 handlers across predict, batch predict, pattern detection,
training start, training runs fetch, training run delete, dataset info,
build dataset, and model load endpoints.
Mark task 5.1 as completed in tasks.md.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>