Parse forwarded email bodies to extract original recipients

[bokelley]

Summary

When users forward emails to [email protected], the actual prospect recipients are in the email body as quoted headers, not in the webhook TO/CC fields. This adds a parser to extract them.

• Add forwarded-email-parser.ts utility with detection for Gmail, Apple Mail, and Outlook forwarding formats
• Integrate into handleProspectEmail() to merge extracted recipients with existing TO/CC
• Add 39 unit tests covering parsing, edge cases, and security

Security improvements (from code review)

• Added MAX_BODY_SIZE (1MB) limit to prevent DoS on large emails
• Rewrote parseHeaderValue to use iterative approach (avoids ReDoS vulnerability)
• Fixed unbalanced bracket handling in splitAddresses
• Added tests for XSS-like display names and large recipient lists

Example

When you forward an email like:

---------- Forwarded message ---------
From: Brian O'Kelley <[email protected]>
To: John Lee <[email protected]>
Cc: Brown, Jason A <[email protected]>, Klippel, Rob <[email protected]>
Subject: Re: Meeting w/Scope3/adcp/charter

The system now extracts all those Charter contacts and creates contact records for them.

Test plan

• Unit tests pass (39 tests)
• TypeScript compiles
• Manual testing with real-world email examples
• Deploy to staging and forward a test email

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