v2.1.1 — Webhooks, German locale, PDF fix

Changelog

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[2.1.1] — 2026-05-18

Added

• Webhook callback support — pass an optional webhook_url in
  POST /api/scan; a POST is delivered to that URL when the scan
  reaches a terminal state. Signed with X-Prism-Secret when
  WEBHOOK_SECRET is set. Private/loopback hosts are rejected.
  Docs: docs/ARCHITECTURE.md (issue #18).
• OPSEC category tooltips — hover over a category in the score bar
  to see a one-line explanation of what it measures (issue #17).
• Alt+T keyboard shortcut to toggle dark/light theme. Topbar
  tooltip updated with the hint (issue #15).
• German (DE) locale — full UI translation; language switcher now
  cycles EN → RU → DE and auto-detects from navigator.language
  (issue #12).
• AI summary copy button refactored to share the global
  copyValue + toast mechanism (PR #19 follow-up).

Changed

• PDF export switched from WeasyPrint (52.5, broken on Windows
  without GTK) to xhtml2pdf (pure-Python). A dedicated
  PDF-friendly template is used so output is stable across OSes.

Fixed

• PDF export endpoint no longer returns 501 / install errors on
  Windows. Generated PDFs render OPSEC score, findings, WHOIS, DNS,
  GeoIP, subdomains, threat intel and phone data correctly.