docs: add email configuration documentation for invitation and password reset

[inkeep]

Summary

Updates documentation to cover the new email integration feature from PR #2021.

Changes

Authentication Documentation (agents-docs/content/deployment/(docker)/authentication.mdx)

• Added Email (Optional) environment variables section with all SMTP/Resend configuration options
• Added Configuring Email (Optional) section explaining:
  • Email is optional with graceful degradation
  • Two configuration options: Resend (cloud) or generic SMTP
  • Local development setup with Mailpit
  • Features enabled when email is configured (automatic invitations, forgot password)
• Added troubleshooting entry for "Forgot password link not showing"

Local Development Documentation (agents-docs/content/deployment/(docker)/docker-local.mdx)

• Added Testing Email Locally section explaining Mailpit usage
• Updated service list to include Mailpit Web UI

Related PR

• Feature PR: feat: email integration for BetterAuth callbacks #2021 (feat: email integration for BetterAuth callbacks)

---

cc @nick-inkeep for review

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Project	Deployment	Actions	Updated (UTC)
agents-api	Ready	Preview, Comment	Feb 16, 2026 0:52am
agents-docs	Ready	Preview, Comment	Feb 16, 2026 0:52am
agents-manage-ui	Ready	Preview, Comment	Feb 16, 2026 0:52am