feat: add API endpoints for downloading certificate and audit log PDFs (#3025)

Add V2 API routes to download an envelope's certificate and audit log
separately, and align the internal cert/audit log downloads to use
envelopeId.

Enforces document visibility via getEnvelopeWhereInput and loads field
signatures so certificates render correctly.

packages/trpc/server/envelope-router/download-envelope-certificate-pdf.ts

@@ -0,0 +1,23 @@
+import { authenticatedProcedure } from '../trpc';
+import {
+  downloadEnvelopeCertificatePdfMeta,
+  ZDownloadEnvelopeCertificatePdfRequestSchema,
+  ZDownloadEnvelopeCertificatePdfResponseSchema,
+} from './download-envelope-certificate-pdf.types';
+
+export const downloadEnvelopeCertificatePdfRoute = authenticatedProcedure
+  .meta(downloadEnvelopeCertificatePdfMeta)
+  .input(ZDownloadEnvelopeCertificatePdfRequestSchema)
+  .output(ZDownloadEnvelopeCertificatePdfResponseSchema)
+  .query(({ input, ctx }) => {
+    const { envelopeId } = input;
+
+    ctx.logger.info({
+      input: {
+        envelopeId,
+      },
+    });
+
+    // This endpoint is purely for V2 API, which is implemented in the Hono remix server.
+    throw new Error('NOT_IMPLEMENTED');
+  });