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>

tests/unit/validators/document-templates.test.ts

@@ -0,0 +1,61 @@
+import { describe, expect, it } from 'vitest';
+
+import { createTemplateSchema } from '@/lib/validators/document-templates';
+
+const baseInput = {
+  name: 'Tmpl',
+  templateType: 'custom' as const,
+  bodyHtml: '<p>x</p>',
+};
+
+describe('createTemplateSchema — mergeFields allow-list', () => {
+  it('accepts valid tokens from the catalog', () => {
+    const parsed = createTemplateSchema.parse({
+      ...baseInput,
+      mergeFields: ['{{client.fullName}}', '{{yacht.name}}', '{{berth.mooringNumber}}'],
+    });
+    expect(parsed.mergeFields).toEqual([
+      '{{client.fullName}}',
+      '{{yacht.name}}',
+      '{{berth.mooringNumber}}',
+    ]);
+  });
+
+  it('rejects deprecated tokens that lived on `clients` before the refactor', () => {
+    const result = createTemplateSchema.safeParse({
+      ...baseInput,
+      mergeFields: ['{{client.yachtName}}'],
+    });
+    expect(result.success).toBe(false);
+    if (!result.success) {
+      expect(result.error.issues[0]?.message).toMatch(/Unknown merge tokens.*client\.yachtName/);
+    }
+  });
+
+  it('rejects unknown tokens with a helpful message listing them', () => {
+    const result = createTemplateSchema.safeParse({
+      ...baseInput,
+      mergeFields: ['{{client.fullName}}', '{{not.a.token}}', '{{also.bogus}}'],
+    });
+    expect(result.success).toBe(false);
+    if (!result.success) {
+      expect(result.error.issues[0]?.message).toContain('not.a.token');
+      expect(result.error.issues[0]?.message).toContain('also.bogus');
+    }
+  });
+
+  it('defaults mergeFields to an empty array when omitted', () => {
+    const parsed = createTemplateSchema.parse(baseInput);
+    expect(parsed.mergeFields).toEqual([]);
+  });
+
+  it('accepts an empty mergeFields array', () => {
+    const parsed = createTemplateSchema.parse({ ...baseInput, mergeFields: [] });
+    expect(parsed.mergeFields).toEqual([]);
+  });
+
+  it('allows the new `eoi` templateType', () => {
+    const parsed = createTemplateSchema.parse({ ...baseInput, templateType: 'eoi' });
+    expect(parsed.templateType).toBe('eoi');
+  });
+});