PM-5433: Fix profile subtrack summary counters

[jmgasper]

What was broken
AI Engineering and Data Science subtrack summary cards could show 0 submissions, and AI Engineering detail headers could show 0 wins, even when the profile history showed challenge activity and winning placements.

Root cause
The profiles UI rendered aggregate counters directly from member stats rows. Some unified stats rows expose challenge/rating history while their aggregate win or submission counters are missing or left at zero.

What was changed
Added a shared subtrack summary helper that preserves positive aggregate counters, falls back to history placement wins when aggregate wins are zero, and falls back to history/challenge counts when submission counters are zero. Track and subtrack views now use that helper for cards and detail summaries.

Any added/updated tests
Updated useFetchActiveTracks specs to cover zero-submission fallback and AI Engineering history-derived wins/submissions.

Validation

• yarn test:no-watch src/apps/profiles/src/hooks/useFetchActiveTracks.spec.tsx passed.
• yarn lint passed.
• yarn run build passed with existing CRA warnings.
• yarn test:no-watch was run for the full suite and failed in unrelated work/wallet specs outside profiles.