Interface web cartographique: COG + TiTiler + viewer MapLibre

- Ajout de convert_to_cog() et generate_cog_metadata() dans rendering.py
- Nouveau module viewer.py: génération HTML MapLibre GL JS avec couches et opacité
- Nouveau module server.py: serveur FastAPI avec TiTiler pour tuiles COG
- Pipeline: étapes 5 (COGs) et 6 (viewer web) après le rapport PDF
- CLI: flag --no-viewer pour désactiver la génération du viewer
- run.sh: commande 'serve' pour démarrer le serveur sur port 8000
- Dockerfile: ajout de rio-cogeo, titiler.core, fastapi, uvicorn, piexif
- setup.py: point d'entrée lidar-server

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

CLAUDE.md

@@ -18,6 +18,8 @@ All commands run inside Docker. Use `./run.sh` as the primary interface.
 ./run.sh -g --file LHD_FXX_1000_6882_PTS_LAMB93_IGN69.copc  # Single file
 ./run.sh --ground-classification pmf            # Force PMF ground classification
 ./run.sh -g --keep-tif                          # Keep intermediate TIFF files
+./run.sh -g --no-viewer                         # Skip web viewer generation
+./run.sh serve                                  # Start web map server
 ./run.sh                                        # Print help (no args)
 ```
 
@@ -37,7 +39,9 @@ docker run --rm --gpus all -v $(pwd)/input:/data/input:ro -v $(pwd)/output:/data
 - **`visualizations.py`** — 15 `generate_*` functions + 2 IGN overlay lambdas. All take `(dem_file, basename, vis_dir, resolution)` and return a TIF path or None.
 - **`gpu.py`** — CuPy/numpy abstraction: `HAS_GPU`, `to_gpu()`, `to_cpu()`, `xp_gaussian_filter()`, `xp_uniform_filter()`, `xp_minimum_filter()`, `gpu_cleanup()`. Falls back to CPU gracefully.
 - **`ign.py`** — IGN WMTS tile download + overlay generation for orthophoto and topographic maps.
-- **`rendering.py`** — `COLORMAPS` dict maps filename keywords to (cmap, title, legend, description). `tif_to_png()` converts TIF→WebP with legend/scale/north arrow. `generate_pdf_report()` creates A3 PDF.
+- **`rendering.py`** — `COLORMAPS` dict maps filename keywords to (cmap, title, legend, description). `tif_to_png()` converts TIF→WebP with legend/scale/north arrow. `convert_to_cog()` converts TIF→Cloud Optimized GeoTIFF. `generate_cog_metadata()` creates metadata JSON for web viewer. `generate_pdf_report()` creates A3 PDF.
+- **`viewer.py`** — Generates MapLibre GL JS HTML viewer with layer controls, opacity sliders, and IGN/OSM basemaps.
+- **`server.py`** — TiTiler-based Starlette server for serving COG tiles and viewer HTML. Entry point via `python -m lidar_pipeline.server`.
 
 ### Adding a visualization
 
@@ -68,6 +72,7 @@ Uses `ProcessPoolExecutor` with `'spawn'` start method (required for CUDA). Each
 - **Language**: UI messages and comments in French. Code identifiers in English.
 - **Logging**: Use `logger = logging.getLogger("lidar")`. Prefix per-file logs via `_file_filter.basename`.
 - **GPU pattern**: `arr_gpu = to_gpu(arr)` → compute → `result = to_cpu(arr_gpu)` → `gpu_cleanup()` between visualizations.
-- **Output format**: Visualizations saved as WebP (not PNG). TIFF intermediates deleted unless `--keep-tif`. PDF reports use `PILImage.open().convert('RGB')`.
+- **Output format**: Visualizations saved as WebP (not PNG). TIFF intermediates deleted unless `--keep-tif` or viewer enabled. COGs generated for web viewer by default. PDF reports use `PILImage.open().convert('RGB')`.
+- **Web viewer**: MapLibre GL JS + TiTiler. COGs served as raster tiles. `./run.sh serve` starts server on port 8000.
 - **Flow accumulation**: Uses numba JIT for D8 accumulation loop. Falls back to pure Python if numba unavailable.
 - **Tests**: Run only inside Docker via `./run.sh --test`. Synthetic DEM fixture in `tests/conftest.py`.