feat: add language-specific causes of death

[mvanhorn]

What changed

• Added 8 language-specific cause-of-death rules to determineCauseOfDeath() in src/lib/scoring.ts
• PHP, Ruby, Python, Perl, Java, Go, Rust, C++ each get their own cause when the repo has been inactive for 365+ days
• Follows the exact same pattern as the existing JavaScript rule

Why

Issue #10 requested language-specific causes. The only language-aware rule was JavaScript ("Lost in dependency hell"). Repos in other languages now get ecosystem-appropriate causes instead of generic fallbacks.

Checklist

• I tested my change locally (npm run lint and npm test)
• I kept the scope focused and avoided unrelated refactors
• I updated docs/screenshots if behavior or UI changed
• I confirmed no secrets are added

Closes #10

This contribution was developed with AI assistance (Codex).

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