…r cross-links

The existing 1,072-line README is the most thorough among all author's repos.
This PR adds what was missing without rewriting the strong content already there.

Added (preserving everything that was already strong)
- Two real-world bot screenshots in a "What it looks like" gallery placed right
  after badges, before the Table of Contents — readers see what the bot
  actually does before reading the architecture
  - 01-onboarding-and-vpn.webp — three-screen onboarding flow (greeting,
    privacy disclaimer, VPN-client picker)
  - 02-scan-and-report-delivery.webp — three-screen scan flow (start,
    VPN-key delivery modes, final report with HTML attachment)
- Sample scan report in two formats:
  - docs/reports/sample-scan-report.md — translated and anonymised real
    report (3 CRITICAL findings: SSH/Telnet/RTSP, 6 HIGH-severity threat
    IPs, traffic stats, recommendations) — Beginner-level rendering
  - docs/reports/sample-scan-report.html — same content as standalone
    HTML with inline dark-theme CSS, mobile-friendly — matches the file
    format the bot actually delivers
- Limitations & known failure modes section — 8 honest constraints
  (encrypted-payload blindness, JA3 evasion, detection lag, mobile-only,
  network-side only, VPN-trust requirement, false positives, no on-device
  remediation) — critical for a security tool's credibility
- Contact section with 4 explicit channels: live bot, Telegram for general,
  GitHub Issues for bugs/rules, email for security researchers /
  responsible disclosure / press / commercial
- Related — Claude Code ecosystem section cross-linking to all 7 sister
  repos by the same author (anti-regression-setup, ai-context-hierarchy,
  claude-statusline, notebooklm-claude-workflows, lingua-companion,
  diabot, ghost-showcase)
- Author signature expanded — full name (Nick Podolyak) + GitHub / Habr /
  dev.to / Telegram links — matches sister-repo standard
- Three new badges: Stars, Validate CI, "@secure_scanbot LIVE"
- CHANGELOG.md (Keep a Changelog) reconstructing showcase history
  (0.1.0 initial → 0.2.0 this PR) plus inline bot v2.3 changes
- CONTRIBUTING.md with Phase-2 readiness priorities (detection rules,
  manufacturer telemetry mapping, locales, Docker hardening, iOS rules,
  STIX2/MISP integrations) and explicit responsible-disclosure clause
- .github/workflows/validate.yml — LICENSE/CHANGELOG presence, every
  docs/* asset referenced from READMEs exists, HTML samples parse,
  internal Markdown links resolve, screenshot files are non-empty
- README.ru.md mirrored: same screenshots gallery, sample-report
  callout, Limitations, Contacts, Related, expanded author

Operational fix (separately, on production VPS)
- security-scanner-bot.service was crash-looping with status=203/EXEC
  since 2026-04-15 06:46 UTC because /root/security-scanner/venv/ had
  been removed from disk. systemd attempted 170,678 restarts before
  this fix. The venv has been recreated, dependencies reinstalled
  (aiogram 3.4.1, aiohttp 3.9.3, aiosqlite 0.19.0, nest_asyncio, plus
  the analysis stack), and the service is now active polling. Bot is
  live again at @secure_scanbot. Documented in CHANGELOG 0.2.0.

Excluded (deliberately)
- No rewrite of the existing 1,072-line README content — it was already
  the strongest among all author's repos (origin story, 4-layer detection
  engine, comparison table, real case study, AI adaptive reports). This
  PR is additive, not destructive.
- Default branch rename master→main deferred — invasive, affects
  external bookmarks
- awesome-claude-code submission — channel locked for non-collaborators

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>