feat(documents): Phase A schema + service skeletons

Adds Phase A data model deltas to documents/templates and the new
document_watchers table. Introduces createFromWizard/createFromUpload
stubs, getDocumentDetail aggregator, cancelDocument flow, signed-doc
email composer, reservation agreement context, and notifyDocumentEvent
fan-out. Validator update accepts new template formats with html-only
bodyHtml requirement. EOI cadence backfilled to 1 day to preserve
current effective behaviour.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/services/document-templates.ts

@@ -432,8 +432,14 @@ export async function resolveTemplate(
     throw new ValidationError(`Missing required merge field values: ${missing.join(', ')}`);
   }
 
+  // HTML body is required for the html template format; non-html formats
+  // resolve elsewhere (see template_format dispatch in PR6).
+  if (template.bodyHtml === null) {
+    throw new ValidationError('Template has no HTML body to render');
+  }
+
   // Interpolate all tokens
-  let resolved = template.bodyHtml;
+  let resolved: string = template.bodyHtml;
   for (const [token, value] of Object.entries(tokenMap)) {
     // Escape token for use in regex
     const escaped = token.replace(/[{}]/g, '\\$&');