feat: increase RTT from 18 to 19

- Update LeaveBalance model default rtt_total to 19
- Update all tests to verify 19 RTT instead of 18
- Update documentation (design and technical plan)
- Update run.py to bind to 0.0.0.0 for external access
- Update CLAUDE.md deployment instructions

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -21,8 +21,9 @@ python -m venv .venv
 # Run a single test
 .venv/bin/python -m pytest tests/test_routes.py::test_create_entry -v
 
-# Production (Gunicorn)
-SECRET_KEY=<secret> ./start.sh
+# Production (systemd) — déployé dans /var/www/tableau-de-bord-pro/
+sudo systemctl edit --full tableau-de-bord-pro  # configurer SECRET_KEY
+sudo systemctl restart tableau-de-bord-pro
 
 # Git commit (GPG signing désactivé — pinentry inaccessible dans cet env)
 git -c commit.gpgsign=false commit -m "..."