feat(18-02): GET and POST handlers at /api/templates

- GET lists active templates (archivedAt IS NULL) with LEFT JOIN for formName
- GET computes fieldCount server-side from signatureFields.length per D-12
- POST validates name + formTemplateId, verifies FK exists, returns 201
- Both handlers auth-gated with auth() per D-11

teressa-copeland-homes/src/app/api/templates/route.ts

@@ -0,0 +1,68 @@
+import { auth } from '@/lib/auth';
+import { db } from '@/lib/db';
+import { documentTemplates, formTemplates } from '@/lib/db/schema';
+import type { SignatureFieldData } from '@/lib/db/schema';
+import { eq, isNull } from 'drizzle-orm';
+
+export async function GET() {
+  const session = await auth();
+  if (!session) return new Response('Unauthorized', { status: 401 });
+
+  const rows = await db
+    .select({
+      id: documentTemplates.id,
+      name: documentTemplates.name,
+      formTemplateId: documentTemplates.formTemplateId,
+      formName: formTemplates.name,
+      signatureFields: documentTemplates.signatureFields,
+      createdAt: documentTemplates.createdAt,
+      updatedAt: documentTemplates.updatedAt,
+    })
+    .from(documentTemplates)
+    .leftJoin(formTemplates, eq(documentTemplates.formTemplateId, formTemplates.id))
+    .where(isNull(documentTemplates.archivedAt));
+
+  const result = rows.map((r) => ({
+    id: r.id,
+    name: r.name,
+    formTemplateId: r.formTemplateId,
+    formName: r.formName,
+    fieldCount: ((r.signatureFields as SignatureFieldData[] | null) ?? []).length,
+    createdAt: r.createdAt,
+    updatedAt: r.updatedAt,
+  }));
+
+  return Response.json(result);
+}
+
+export async function POST(req: Request) {
+  const session = await auth();
+  if (!session) return new Response('Unauthorized', { status: 401 });
+
+  const body = await req.json() as { name?: string; formTemplateId?: string };
+
+  if (!body.name || !body.formTemplateId) {
+    return Response.json(
+      { error: 'name and formTemplateId are required' },
+      { status: 400 }
+    );
+  }
+
+  // Verify form template exists
+  const form = await db.query.formTemplates.findFirst({
+    where: eq(formTemplates.id, body.formTemplateId),
+  });
+  if (!form) {
+    return Response.json({ error: 'Form template not found' }, { status: 404 });
+  }
+
+  const [template] = await db
+    .insert(documentTemplates)
+    .values({
+      name: body.name,
+      formTemplateId: body.formTemplateId,
+    })
+    .returning();
+
+  return Response.json(template, { status: 201 });
+}