Add C-CSF planar boundary geometry

[svchb]

Summary

• extend CorrectedCSFSurfaceNormal with an optional finite contact angle
• add the C-CSF planar boundary-integral moment, eigenvalue-gradient, color-gradient, and curvature terms from Vergnaud et al. (2022)
• apply the published distance-weighted contact-normal correction near the wall
• add explicit per-particle surface_measure quadrature data to dummy-particle boundaries and validate the supported configuration
• retain the existing no-contact free-surface path without boundary-only cache allocations
• add metadata, documentation, migration notes, and planar/hemispherical geometry regressions

Stack

Depends on #1269, which depends on #1268 and #1252. Fork branches cannot be selected as bases for pull requests into the upstream repository, so this PR targets main and temporarily shows the preceding commits.

Review-only diff: svchb/TrixiParticles.jlOpen@rebuild/morris-csf-interface...rebuild/ccsf-boundary-geometry

Scope

This PR implements C-CSF boundary geometry only. It supports one fluid system with stationary planar dummy-particle WallBoundarySystems, explicit face measures and normal offsets, and a 3D WendlandC2Kernel. Hydrodynamic continuity, pressure, and viscosity coupling still use the configured dummy-particle model; the full hydrodynamic BIM formulation is not included. Moving walls, rigid boundaries, general curved BIM faces, and ghost-particle C-CSF geometry are intentionally excluded.

Verification

• C-CSF free-surface geometry tests: 18/18
• C-CSF planar boundary-geometry tests: 22/22
• C-CSF hemispherical-contact tests: 4/4
• C-CSF 3D curvature tests: 4/4
• aggregate surface-tension tests: 97/97
• WCSPH system tests: 224/224
• EDAC system tests: 96/96
• rigid-system tests: 182/182
• RHS tests: 1197/1197
• particle-packing tests: 8/8
• Aqua passed
• documentation build passed
• complete unit target: 22883 passed; only the established baseline set remained (1 failed, 3 errored)
• JuliaFormatter 2.1.1 and git diff --check passed

[svchb]

Dependency note: this sibling C-CSF boundary layer should inherit the #1282 surface_method API when the #1268/#1269 base is refreshed. The boundary-integral geometry remains specific to this PR; no additional integration dependency or stack layer is planned.