feat(example-doc-vault): configure Supabase Auth, RBAC Field-Level Security and S3 presigned storage

[crapougnax]

Part of parent story #36.

🎯 Goal

Implement identity verification, role-based Field-Level Security, and cloud object storage for the Document Vault tutorial.

📋 Specification

1. Authentication with @quatrain/auth-supabase:
   • Register SupabaseAuthAdapter into Auth.addProvider(supabaseAdapter, 'supabase', true).
   • Validate JWT tokens and resolve user identities into RbacUserContext.
2. Granular Field-Level Security (FLS) with @quatrain/auth-rbac:
   • Role definitions: viewer, author, approver, admin-finance.
   • Protect financialAmount field using rbac.sanitizeRead('documents', payload, userContext) (hidden for non-finance users).
3. S3 Storage with @quatrain/storage-s3:
   • Register S3StorageAdapter with MinIO / Scaleway S3 / AWS S3.
   • Generate secure presigned upload and download URLs for PDF documents.