EM-02: Set up the Kit sender identity and DNS authentication (SPF, DKIM, DMARC)

Source document: .agents/email-migration-and-sequence-plan.md (§3 “Phase 2: Account, DNS & Deliverability Setup”)
Owner: 👤 User only
Priority: High
Status: Unverified (the agent can’t access Kit or the domain’s DNS manager)
Depends on: None

[!IMPORTANT] User-only task: Reece needs to do this. It needs the Kit account and the DNS provider for jackhighbowls.com.

Task

Make sure emails from Kit are authenticated so they land in the inbox. Many bowlers use strict ISP inboxes: BT Internet, Sky, TalkTalk, Yahoo, Gmail.

In Kit, set the “From” name to Reece at Jack High Bowls and the sending address to reece@jackhighbowls.com. Never send bulk email from a free @gmail.com address.
Verify jackhighbowls.com as a sending domain in Kit, and add the DKIM and SPF records Kit provides to the DNS manager.
Add or confirm a DMARC record at _dmarc.jackhighbowls.com:
```
v=DMARC1; p=none; rua=mailto:reece@jackhighbowls.com
```
Keep any existing SPF include for other services. A domain must have only one SPF TXT record; merge the includes into it.

Kit shows the domain as verified/authenticated.
SPF, DKIM and DMARC records resolve publicly (check with MXToolbox or dig TXT).
A test broadcast to a Gmail and a Yahoo inbox shows spf=pass, dkim=pass and dmarc=pass in the message headers.