167 seedmock data fixes improvements

[dboghra]

Summary

Closes #167

What changed:
Brief summary of the change (2-3 sentences max).
Added a female athlete (Olga Almazova) to seed data and fixed the 400m hurdle mock data generator. The fixed generator produces strictly alternating foot contacts and correctly positioned hurdle times.

Why:
What problem this solves or requirement it addresses.
The seed data only had male athletes, and the existing hurdle_400m.csv had two bugs visible in the visualizations, both feet registering ground contact simultaneously on every stride.

Technical decisions worth noting:
Any non-obvious choices and their rationale.
Screenshots are not working on my computer for some reason.

AI disclosure: Note what was AI-assisted vs. hand-written.
Mock data generator rewrite, hurdle timing calculations, Olga's seed data (athlete record + 400mH stride metrics) were all AI-assisted.

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Screenshot

Notes