Extracts the MERGE_FIELDS catalog out of the document-templates service
into src/lib/templates/merge-fields.ts so the Zod validator can import
it without circular deps. createTemplateSchema now refines mergeFields
against VALID_MERGE_TOKENS — unknown tokens (including the deprecated
`{{client.yachtName}}` / `{{client.companyName}}` family) are rejected
at template creation time with a message naming the offenders.
Adds the missing `eoi` value to templateType enum so seeded EOI rows
round-trip through the validator. Drops the historical "Removed (PR 11):"
comment from the catalog (per project convention against `// removed`
markers).
6 new validator unit tests; 652/652 green.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
