OAuth phase 2: X/IG token exchange, claim_result in DB, callback redirects, hide claim buttons when claimed

Claim buttons on result page + scoring unit tests ...

- result.html/result.js: Claim via X / Instagram buttons wired to
  /auth/{x,ig}/start, graceful 503 hint until apps are registered
- scripts/test_scoring.py: 17 unit tests (raw_score, sanity_check bot
  flags, IQ bounds, percentile extremes, categories, calibration
  fallback) — all passing

VerIQ v1 MVP: FastAPI backend, 40-task bank, frontend, Ed25519 signing ...

- backend: main.py (API + sessions + rate limit), scoring.py (weighted
  z-score normalization, sanity checks), signing.py (Ed25519 canonical
  payload signing), db.py (SQLite WAL, results + events)
- content: questions.json v1.0.0 (40 original tasks, 4 categories,
  SVG figures), calibration.json placeholder
- frontend: brutalist dark theme, test engine with timer/resume,
  result page with share links, public verify page
- docs: SPEC.md (product + tech spec, milestones)
- smoke-tested: full cycle start->finish->verify, tamper rejection OK