Add sponsor-focused analytics:
- Sponsor count by level (donut chart)
- Sponsor revenue goal vs actual (budget gauge)
- Configurable
sponsor_target_count and sponsor_revenue_goal on Conference
- Charts on
/manage/<slug>/sponsors/ and reports dashboard
Depends on: #46
Add sponsor-focused analytics:
sponsor_target_countandsponsor_revenue_goalon Conference/manage/<slug>/sponsors/and reports dashboardDepends on: #46