feat(sprint-5-6): live progression metric audit, atomic founding allocation, notifications service, and mentorship API

[ashishsinghbora]

Sprint 5 & 6 Summary

• Live Contributor Progression Audit:
  • Replaced hardcoded progression values with live queries against actual database records (pull_requests, pull_request_reviews, contributions, and issue_claims).
  • No synthetic or mock metrics: prsOpened, prsMerged, issuesResolved, reviewsCompleted, and projectsContributedCount all derive directly from verified platform evidence.
• Atomic Founding 1,000 Allocation:
  • Audited and reinforced claimFoundingMembership with optimistic concurrency retry loops to prevent race conditions during concurrent PR merges while preserving strict sequential numbering (1 to 1000).
• In-App Notifications Service (src/lib/notifications/service.ts):
  • Created notification generation, listing, and read status management.
  • Endpoints: GET /api/notifications, POST /api/notifications/[id]/read.
• Mentorship Assistance Request Engine (src/lib/mentorship/service.ts):
  • Allows contributors to request guidance on specific issues and projects.
  • Mentors and maintainers can list, review, and reply to requests with automated in-app notifications dispatched to students.
  • Endpoints: GET /api/mentors/requests, POST /api/mentors/requests, POST /api/mentors/requests/[id]/reply.
• Verification Battery:
  • 16 test files passed, 55/55 tests green (100%).
  • 0 lint errors, 0 type errors, production build validated.