Improve discovery scoring explanation

[nikkkkj]

Fixes #3.

Summary

• Replace the compact discovery score formula with named score components
• Add comments explaining the funding, activity, recency, and reward weights
• Show score breakdown details in each bounty card
• Add deterministic reward tie-break sorting
• Include the existing minimal form validation compile fix so production build is not blocked by the current errors reference

Verification

• npm run lint
• npm run build
• Browser check: opened /discovery, confirmed the ranked list renders with visible score and Funding/Activity/Recency breakdown details

Note: lint/build still report the existing Next.js <img> warning in src/components/leaderboard.tsx, but the build completes successfully.