Sync individual Opportunity amounts via Salesforce integration (not just account-level ARR)

The Salesforce integration currently pulls account-level ARR only. We need to pull revenue from individual Opportunities instead, since the amount at stake differs depending on whether it's a renewal or an upsell scenario tied to a specific deal.

Ideally we could choose between account-level ARR or Opportunity-level amount depending on context.

Raised on a demo call by Toby Penn at WitnessAI.