Fix generator rewards truncated by global 1,000-outcome cap

[dylanuys]

Summary

• Remove the implicit global 1,000-outcome cap from generator reward statistics so all eligible outcomes in the validator's 24-hour window contribute.
• Keep explicit limits available for diagnostic callers; preserve completion-time filtering, per-modality pass rates, and exclusion of no_answer outcomes.
• Bump both version strings to 5.0.8 for validator auto-updates; keep 5.0.8 when merging the updated testnet branch.

The cap could crowd out a miner's verified images with newer outcomes from other miners. In the investigated snapshot, 3,120 eligible outcomes were reduced to roughly seven hours of history, dropping two verified images still inside the intended 24-hour window.

Validation

• SQLite regressions cover more than 1,000 newer outcomes, older qualified image rewards, the exact time cutoff, excluded states/no-answers, and explicit limits through the reward-facing wrapper.
• Combined testnet suite: 212 passed. CI-selected Ruff checks, lockfile consistency, and git diff --check passed. Callback startup and signed-upload/retry smoke tests passed with the pinned security dependencies.