V94: Add Google Drive metadata columns to Document Creator tables.

Adds columns needed for local DB mirroring of Google Drive file metadata:

• google_doc_id (VARCHAR(255)) on templates, documents, and headers_footers
• status (VARCHAR(20), DEFAULT 'published') on documents (templates already have it)
• path (VARCHAR(500)) on templates and documents for the accepted folder path
• folder_id (VARCHAR(255)) on templates and documents for the accepted parent folder
• Partial unique indexes on google_doc_id WHERE google_doc_id IS NOT NULL

All operations are idempotent.