Add sovereign AI installer script

[Tibo2403]

Summary

• Add a structured Bash installer for Open WebUI + Ollama.
• Keep bilingual FR/EN messages.
• Add safer shell settings, Docker availability checks, container restart/idempotency handling, configurable variables, and automatic GPU detection.
• Use ollama pull instead of ollama run for model installation to avoid starting an interactive chat during setup.

Validation

• bash -n /tmp/install_ia_souveraine.sh

Notes

• Runtime deployment with Docker/GPU was not executed in this environment.
• GPU can be controlled with GPU_MODE=auto|on|off; default is auto.