log: ListDocumentFoldersAsync prints folder count on success

When the case-scoped query fails (e.g. tenant rejects parentId in
where), the ViewModel falls back to ListDocumentFoldersAsync — but a
success path with N=0 was silent, leaving the user wondering why the
dropdown stayed empty. Add an INF line so the log shows whether
N folders came back, so 0-folder tenants are obvious from a glance.

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

src/OutlookAddin.Core/Services/EspoCrmClient.cs

@@ -390,9 +390,13 @@ namespace MarcusLaw.OutlookAddin.Core.Services
         {
             try
             {
-                return await GetJsonAsync<EspoListResponse<DocumentFolder>>(
+                var result = await GetJsonAsync<EspoListResponse<DocumentFolder>>(
                     "DocumentFolder?orderBy=name&order=asc&maxSize=200",
                     cancellationToken).ConfigureAwait(false);
+                _logger.Information(
+                    "ListDocumentFoldersAsync → {Count} folders in tenant",
+                    result?.List?.Count ?? 0);
+                return result ?? new EspoListResponse<DocumentFolder>();
             }
             catch (Exception ex)
             {