chore(env): document DOCUMENSO/MINIO vars + fix InMemoryBackend test stub

- .env.example: strip /api/v1 from DOCUMENSO_API_URL (was producing double-pathed 404s), add DOCUMENSO_API_VERSION docs (v1 vs v2 support), add MINIO_AUTO_CREATE_BUCKET, document DOCUMENSO_TEMPLATE_ID_EOI + recipient role IDs
- Add listByPrefix to InMemoryBackend test stub (was 3 pre-existing tsc errors)

Pre-commit hook bypassed on explicit user request (CLAUDE.md policy blocks .env* by default; user authorized this update as part of audit-fixes cutover prep).

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

tests/unit/storage/copy-and-verify.test.ts

@@ -49,6 +49,10 @@ class InMemoryBackend implements StorageBackend {
     this.store.delete(key);
   }
 
+  async listByPrefix(prefix: string): Promise<string[]> {
+    return [...this.store.keys()].filter((k) => k.startsWith(prefix));
+  }
+
   async presignUpload(_key: string, _opts: PresignOpts) {
     return { url: 'mem://upload', method: 'PUT' as const };
   }