Restore and verify automated Google Sheets export on Oracle v6

[adhamhaithameid]

Problem

Oracle logs indicate automated Sheets export is skipped because Sheets configuration is missing.

Why it matters

• archival/backup pipeline is effectively disabled
• backup drift checks become incomplete

Scope

• configure required Sheets env/secrets in production
• add startup validation for Sheets config
• add dashboard status for last successful Sheets flush
• add smoke test for sheets export path

Acceptance

• scheduled export runs successfully
• dashboard shows latest successful Sheets flush timestamp
• no "skipping automated Sheets export" warning in normal operation