chore: stop tracking .claude/settings.local.json

This file holds per-user Claude Code permission allowlists and should not
be shared across the team. Adding it to .gitignore and removing from the
index; existing working copies are preserved.

.gitignore

@@ -2,6 +2,9 @@
 .vscode/
 frontend-web/.vscode/
 
+# Claude Code local-only settings (per-user permissions, not shared)
+.claude/settings.local.json
+
 # Local runtime logs and pid files
 .runtime/