Translate the whole project to English and fix outdated comments and help

Comments, docstrings, logs, CLI help, map UI, legends, PDF sheet, scripts,
compose files and AGENTS.md are now English. Data keys stay unchanged
(relief_oriente, densite_sol, visualisations/, API JSON keys, link params).
Wrong comments and help defaults found along the way are corrected.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

requirements.txt

@@ -1,9 +1,9 @@
-# Dépendances Python de l'image complète (Dockerfile) — installées via
+# Python dependencies of the full image (Dockerfile) - installed with
 # `pip install --no-cache-dir -r requirements.txt`.
-# PDAL n'est PAS installé par pip : binaire conda (cf. Dockerfile), invoqué
-# en ligne de commande. L'image webapp légère (Dockerfile.webapp) a sa propre
-# liste minimale (fastapi, uvicorn, Pillow, pyproj).
-# CuPy est installé séparément (cupy-cuda12x) selon la cible CUDA.
+# PDAL is NOT installed by pip: conda binary (see Dockerfile), invoked on the
+# command line. The lightweight map image (Dockerfile.maps) has its own
+# minimal list (fastapi, uvicorn, Pillow, pyproj, reportlab).
+# CuPy is installed separately (cupy-cuda12x) for the CUDA target.
 numpy>=1.24
 scipy>=1.10
 matplotlib>=3.7
@@ -16,7 +16,7 @@ fastapi>=0.110
 uvicorn>=0.29
 pydantic>=2.6
 pyproj>=3.6
-reportlab>=4.0  # Export PDF de la carte (mapserve)
+reportlab>=4.0  # Map PDF export (mapserve)
 
 # Tests (./run.sh --test)
 pytest>=7.4