feat: NLP patch insights + standalone demo mode

- dlib/ai/insights.py: pure-Python NLP analysis that correlates accepted
  AI suggestion operations/keywords/sections with submission outcomes
  (pending_review / published = positive, archived = negative)
- Backend: GET /api/v1/insights route + service + Pydantic schema
- Frontend: InsightsPanel component with bar charts for operation impact,
  section impact, and keyword signal lift scores
- Insights tab added to the version panel; compact preview on doc overview
- NEXT_PUBLIC_DEMO=true makes the webapp fully standalone: loads
  DEMO_DOCUMENTS / DEMO_SUBMISSIONS / DEMO_INSIGHTS from demo-data.ts,
  disables all mutating actions, shows a DEMO badge in the top bar
- apps/webapp/public/demo-cv.docx: static dummy CV (Alex Rivera) for demo
- scripts/gen_demo_cv.py: script to regenerate the demo DOCX
- .env.example: document NEXT_PUBLIC_DEMO flag

https://claude.ai/code/session_01LWxu2qrwY6BRjUFXXn7NiM

.env.example

@@ -56,3 +56,8 @@ AUTHENTIK_CLIENT_SECRET=
 # ── AI tailoring (optional) ───────────────────────────────────────────────────
 # Leave blank to use the built-in rule-based tailoring instead of Claude.
 ANTHROPIC_API_KEY=
+
+# ── Demo mode ─────────────────────────────────────────────────────────────────
+# Set to true to enable standalone demo mode in the webapp.
+# Demo mode uses hardcoded dummy data — no backend or DB required.
+NEXT_PUBLIC_DEMO=false