refactor(templates): merge-field allow-list rejects unknown tokens

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>

src/lib/validators/document-templates.ts

@@ -1,11 +1,25 @@
 import { z } from 'zod';
 
 import { baseListQuerySchema } from '@/lib/api/route-helpers';
+import { VALID_MERGE_TOKENS } from '@/lib/templates/merge-fields';
+
+const mergeFieldsSchema = z
+  .array(z.string())
+  .optional()
+  .default([])
+  .refine(
+    (tokens) => tokens.every((t) => VALID_MERGE_TOKENS.has(t)),
+    (tokens) => {
+      const unknown = tokens?.filter((t) => !VALID_MERGE_TOKENS.has(t)) ?? [];
+      return { message: `Unknown merge tokens: ${unknown.join(', ')}` };
+    },
+  );
 
 export const createTemplateSchema = z.object({
   name: z.string().min(1).max(200),
   description: z.string().max(500).optional(),
   templateType: z.enum([
+    'eoi',
     'welcome_letter',
     'handover_checklist',
     'acknowledgment',
@@ -13,7 +27,7 @@ export const createTemplateSchema = z.object({
     'custom',
   ]),
   bodyHtml: z.string().min(1),
-  mergeFields: z.array(z.string()).optional().default([]),
+  mergeFields: mergeFieldsSchema,
   isActive: z.boolean().default(true),
 });