fix(leadmail): extract from-display via addrs.first.display_name; log payload from

Previous extract_from used message[:from].display_names.first. That
method exists on Mail::Field but its behavior across Mail gem versions
is inconsistent — it sometimes returns a string, sometimes blank. The
canonical Mail gem API for getting the display name of the first
address in a multi-address field is addrs.first.display_name, which
returns the parsed display name reliably.

Without a working display name extraction, our LeadMail payload only
included {email: ...} without the name, so emails arrived showing only
the bare 'dev@leadmagnet.fi' instead of 'Niklas Pull from Lead Magnet
Dev <dev@leadmagnet.fi>'.

Also include the from payload (email + name) in the success log line so
future from-header issues are immediately visible without needing to
check LeadMail's dashboard.

app/mailers/leadmail_delivery.rb

@@ -15,7 +15,10 @@ class LeadmailDelivery
 
     response_data = JSON.parse(response.body)
     message.header['X-LeadMail-Log-ID'] = response_data.dig('data', 'log_id')
-    Rails.logger.info("Email sent via LeadMail: log_id=#{response_data.dig('data', 'log_id')}, to=#{message.to.inspect}")
+    Rails.logger.info(
+      "Email sent via LeadMail: log_id=#{response_data.dig('data', 'log_id')} " \
+      "from=#{payload[:from].inspect} to=#{message.to.inspect}"
+    )
     response
   rescue StandardError => e
     Rails.logger.error("LeadMail delivery failed: #{e.message}\nPayload: #{payload.inspect}")
@@ -51,8 +54,9 @@ class LeadmailDelivery
   end
 
   def extract_from(message)
+    from_field = message[:from]
     from_address = message.from&.first
-    from_display = message[:from]&.display_names&.first
+    from_display = from_field&.addrs&.first&.display_name
 
     {
       email: from_address,