Rename the project to FieldCraft

Crates fieldcraft-*, binaries fieldcraft and fieldcraft-cli, the .fieldcraft file (format tag
fieldcraft/1, manifest fieldcraft.json), FIELDCRAFT_* environment variables, the MCP server
name, egui widget ids (fc_*), the app icon document FieldCraft.icon and its generated family,
docs and licences. No compatibility shim: no files of the earlier name exist.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

crates/solver/tests/common/mod.rs

@@ -5,7 +5,7 @@
 
 use std::collections::BTreeMap;
 
-use modelcraft_model::{
+use fieldcraft_model::{
     BoundaryCondition, Coupling, CouplingKind, Dofs, Elastic, ElementFace, ElementKind, Formulation, Integration, Load, Material, Model, Procedure,
     ReferencePoint, Section, SectionKind, Set, Step, Symmetry, Target,
 };