feat: add PR intelligence

[SamoTech]

Phase 10 — PR Intelligence

• Adds a reusable PR evidence engine.
• Adds /api/pr?repo=owner/name&number=N with Redis caching and rate limiting.
• Adds PR Intelligence dashboard and navigation.
• Reports change size, review state, CI status, age, mergeability, and sensitive-file exposure.
• Adds unit coverage for the evidence engine.

Validation required before merge.

[vercel]

Deployment failed for project devlens with the following error:

Resource is limited - try again in 24 hours (more than 100, code: "api-deployments-free-per-day").

Learn More: https://vercel.com/samotechs-projects?upgradeToPro=build-rate-limit

[chatgpt-codex-connector]

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