Audit Lead Capture + 3-Email Drip

• audit_leads table captures email + marketplace + leak severity from the /audit tool
• 3-email Postmark drip: T+0 "Your results", T+2d "What this means", T+5d "Fix it with Filtrate"
• Admin endpoints: GET /admin/audit-leads, POST /admin/process-drip?step=N
• UTM-tagged utm_source=audit_drip, utm_campaign=lead_nurture on all drip links