chore: ignore *.csproj.lscache LSP artifacts (#261)

Adds `*.csproj.lscache` pattern to `.gitignore` to suppress 16 untracked
LSP artifact files generated by the C# language server.

These files are build/IDE artifacts and should never be committed.

---
🤖 Ralph (Work Monitor) — housekeeping chore

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: mpaulosky

.gitignore

@@ -387,6 +387,7 @@ MigrationBackup/
 
 # IDE / local
 .vscode/
+*.csproj.lscache
 
 # Test output
 coverage/