chore: add Claude Code configuration

- add CLAUDE.md (project description, architecture, domain notes, git workflow)
- add shared .claude/settings.json (allowed commands, .env read protection)
- pin Prisma agent skills in skills-lock.json and document how to restore them
- ignore generated skills, local settings and Postman skills in .gitignore
- add .gitattributes to normalize line endings to LF

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

.gitignore

@@ -55,3 +55,15 @@ report.[0-9]*.[0-9]*.[0-9]*.[0-9]*.json
 
 # Prisma client (regenerated by `prisma generate`, run on npm install)
 /prisma/generated/
+
+# AI agent skills installed from skills-lock.json (keep skills-lock.json committed)
+/.agents/
+/.windsurf/
+/.claude/skills/
+# Claude Code personal settings (.claude/settings.json stays shareable)
+/.claude/settings.local.json
+
+# Postman (skills fetched by `postman init`, personal workspace binding)
+/postman/
+/.postman/
+/AGENTS.md