Firebase Client SDK

| Skill | Description | |-------|-------------| | [firebase-auth](skills/1-Frontend/firebase-client/firebase-auth/) | Firebase Authentication — email/password, OAuth, tokens, custom claims, MFA | | [firebase-firestore](skills/1-Frontend/firebase-client/firebase-firestore/) | Firestore CRUD, queries, real-time listeners, security rules, offline | | [firebase-storage](skills/1-Frontend/firebase-client/firebase-storage/) | Cloud Storage uploads, downloads, signed URLs, security rules, CORS |…