Add zip upload and mapped-path picker for outline import

Sandbox source paths under a configured Imports:RootPath, browse it
from the web dialog, upload a zip that extracts into staging, and
import a single markdown file (agent infers chapter vs character).

src/Novelly.Api/Imports/ImportOptions.cs

@@ -0,0 +1,8 @@
+namespace Novelly.Api.Imports;
+
+public class ImportOptions
+{
+    public const string SectionName = "Imports";
+
+    public string? RootPath { get; set; }
+}