Stability checkpoint Python — runbooks + FR sync + dashboards + renovate base + architect matrix

Achievements vs stable-py-v0.6.1 :
- 3 runbooks SLO : availability + latency + enrichment (unblocks Alertmanager 404s)
- README.fr.md fully synced with EN (TL;DR + SLO badges + Sloth + industrial framing)
- mkdocs index.md refreshed with Sloth + 12 ADRs + cross-repo links
- 'What this proves for senior architect' 8-row matrix (Java had it, Python now too)
- Renovate consolidated via shared base preset + sync script
- Shared submodule SHA bumped (3 new dashboards : SLO breakdown by endpoint,
  latency heatmap, Apdex + SLO review cadence doc + renovate-base.json)

Validation : main pipeline #86 green sha=21e63a0e