chore: add Claude Code configuration (#2)

## Summary
- Add `CLAUDE.md`: project description (K-pop shop backend, buffer in front of Hiboutik), architecture, domain notes, git workflow.
- Add shared `.claude/settings.json` (allowed dev commands, `.env` read protection).
- Pin the Prisma agent skills in `skills-lock.json` (restore with `npx skills experimental_install`, documented in the README).
- Update `.gitignore` (generated skills, local settings, Postman skills) and add `.gitattributes` (LF line endings).

## Note
This branch is based on `feat/customer-addresses-orders`, so the PR also contains the 3 feature commits (addresses, company details, orders) that `CLAUDE.md` describes.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: MastersGame <quentin.duwa1210@gmail.com>
Reviewed-on: #2

.claude/settings.json

@@ -0,0 +1,17 @@
+{
+  "permissions": {
+    "allow": [
+      "Bash(npm run lint)",
+      "Bash(npm run build)",
+      "Bash(npm test)",
+      "Bash(npm run test:e2e)",
+      "Bash(npx jest:*)",
+      "Bash(npx prisma generate --config prisma7.config.ts)"
+    ],
+    "deny": [
+      "Read(./.env)",
+      "Read(./.env.*)",
+      "Bash(cat .env*)"
+    ]
+  }
+}