BlueMesh2D QGIS 4 compatibility

Wraps the BlueMesh2D meshing library as QGIS Processing algorithms: from a bathymetry GeoTIFF to an unstructured triangular mesh, written as a UGRID NetCDF that loads directly as a QGIS mesh layer. The workflow runs as six stages: • 1 - Extract the water polygon (coastline and domain) from the raster. • 2 - Build a gradient-limited element-size raster: depth polynomial, wavelength (Hunt 1979) or a custom Python function, with optional finer detail regions. • 3 - Resample the boundary to the element size, as an editable line layer. • 4 - Generate the mesh: Delaunay or Frontal-Delaunay refinement, optional smoothing and smood orthogonalisation for Delft3D-FM. • 5 - Classify the boundary nodes into open, closed and island, editable in QGIS. • 6 - Export: UGRID NetCDF, Delft3D-FM open-boundary files (.pli / .bc / .ext) or ADCIRC .grd. Each stage produces an ordinary QGIS layer, so every intermediate result can be inspected and hand-edited before the next step; an all-in-one algorithm is also available for a single-dialog run. Step-by-step tutorial (PDF): https://github.com/GeoOcean/BlueMesh2D/blob/develop/docs/Tuto_BlueMesh2D_Santander.pdf Dependencies need no manual setup. On first load the plugin detects what is missing and installs it in one click (Plugins ▸ BlueMesh2D ▸ Check / install dependencies). pip runs in QGIS's own interpreter; on Debian/Ubuntu system Python (PEP 668) the packages go into a plugin-managed virtual environment instead, leaving the system Python untouched. Installing bluemesh2d brings numpy, scipy, shapely, rasterio, matplotlib, netCDF4, xarray and triangle with it.