Release v5.18.0

• chore: bump version to 5.18.0 and update docs (Dries Peeters)
• Fix Android Chromium freeze from Flatpickr mobile-mode init loop (#771). (Dries Peeters)
• Fix instance audit 500s, API edge cases, and smoke-test reliability. (Dries Peeters)
• Add TimeTracker footer watermark to exported PDFs. (Dries Peeters)
• feat(observability): add request IDs, hardening metrics, and Sentry hooks (Dries Peeters)
• ci: add Bandit and pip-audit gates and raise the coverage floor (Dries Peeters)
• chore(ops): harden readiness probes, migrations, and production defaults (Dries Peeters)
• fix(data): harden invoice numbering, timers, and scheduler leadership (Dries Peeters)
• fix(security): harden redirects, SSRF, session rollback, and HTTP timeouts (Dries Peeters)
• chore(deps): bump pyjwt (dependabot[bot])
• chore(deps-dev): bump electron (dependabot[bot])
• docs: restructure README for conversion and add in-app star prompts (Dries Peeters)

📦 Build Status

Desktop Applications

✅ Windows build: Success
✅ Linux build: Success
✅ macOS build: Success

Mobile Applications

✅ Android build: Success
✅ iOS build: Success