Add email-based exclusion rules

• Add new setting ff_nutshell_exclusion_email_patterns (newline-separated regex)
• Admin UI: textarea field “Exclude Emails (Regex Patterns)” with examples and sanitizer
• Form handling: skip all Nutshell actions when submitter email matches any pattern
  • Early return in FF_Nutshell_Form_Handler::create_lead()
  • Safe regex handling (supports /.../i or raw patterns auto-wrapped as case-insensitive)
  • Log invalid regex patterns; log when submissions are excluded (when logging enabled)

Improved owner assignment, note handling, and stability

• More reliable agent→owner mapping
  • Sanitize and reuse agent_email, consistently track owner_id
• Safer lead creation flow and note attribution
  • Use response with explicit success checks, defensive lead_id extraction, final payload and created ID logging, and prepend agent attribution to notes when available
• Support owner on contact create/find
  • Add optional owner_id to create_contact and find_or_create_contact and set links.owner in the request payload
• Preserve note template line breaks in admin
  • Use sanitize_textarea_field specifically for note_template within sanitize_mapping_data to preserve newlines