Add diagnostic logging to email webhook handler

[bokelley]

Summary

• Add diagnostic logging at key checkpoints in the prospect email webhook handler to identify where email tracking is failing
• The webhook processes emails but appears to stop after contact creation without storing activities

Logging Added

• After contact creation: "Created/updated email contacts"
• Before insight extraction: "Starting insight extraction"
• After insight extraction: "Completed insight extraction"
• Before activity storage: "Storing email activity"
• After activity storage: "Stored email activity, linking contacts"
• After contact linking: "Linked contacts to email activity"

Test plan

• Deploy and send a test email to addie+prospect@updates.agenticadvertising.org
• Check fly logs to see which checkpoint is reached before failure
• Use the new logging info to identify and fix the root cause

🤖 Generated with Claude Code