feat: add Docker deployment configuration

Add backend and frontend Dockerfiles, docker-compose setup with nginx
reverse proxy, .dockerignore files and Makefile for dev/prod workflows.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Makefile

@@ -0,0 +1,17 @@
+.PHONY: dev_back dev_front dev docker
+
+# Backend avec auto-reload uvicorn
+dev_back:
+	uv run plesna-gerance serve --reload
+
+# Frontend avec hot-reload Vite
+dev_front:
+	cd frontend && npm run dev
+
+# Lance les deux en parallèle
+dev:
+	$(MAKE) dev_back & $(MAKE) dev_front & wait
+
+# Build et lance via podman-compose
+docker:
+	podman-compose up --build