fix: AI worker crash-proof + GDPR/hosting/accessibility analysis

AI worker fixes (root cause of "nothing reaches Replicate"):
- Worker task died silently — no exception handler around while loop
- Added try/except around entire loop body with exc_info logging
- Added watchdog task that restarts dead workers every 10 seconds
- ensure_workers_alive() called on every /api/ai/assess/batch POST
- _assess_one() is now a top-level function (not closure) — avoids
  subtle scoping bugs with async inner functions in while loops
- /api/ai/debug endpoint: shows worker alive status, task exception,
  last 10 queue entries — browse to /api/ai/debug to diagnose
- /api/ai/worker/restart endpoint + UI button
- "Restart AI worker" button + "Debug AI queue" link in enrichment tab

site_analyzer.py — new signals:
- IP resolution + ip-api.com for ASN, org, ISP, host country
- EU hosting detection (27 EU + EEA + adequacy countries)
- GDPR: detects Cookiebot, OneTrust, CookiePro, Osano, Iubenda,
  Borlabs, CookieYes, Complianz, Usercentrics + text signals
- Privacy policy and GDPR text presence
- Accessibility: html lang missing, images without alt count,
  skip nav link, empty links, inputs without labels

Gemini prompt additions:
- Hosting section: IP, ASN, org/ISP, EU vs non-EU flag
- GDPR section: cookie tool, notice, privacy policy
- Accessibility section: all quick-scan results
- New output fields: hosting_notes, gdpr_compliance,
  accessibility_issues[]

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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