Add CLAUDE.md, replace Makefile with Justfile, remove .junie

- Add CLAUDE.md with project overview, commands, architecture, and domain entity docs
- Remove Makefile in favour of the existing Justfile
- Remove .junie/AGENTS.md (knowledge transferred to CLAUDE.md)
- Update .gitignore: drop .junie/ entries, add .claude/settings.local.json
- Minor doc fixes in config/reference.php (typo, type correction)

.gitignore

@@ -72,10 +72,8 @@ Icon
 /.idea/
 /.vscode/
 
-# Junie
-!/.junie/
-/.junie/memory/
-/.junie/plans/
+# Claude Code
+/.claude/settings.local.json
 
 # Windows
 Thumbs.db