Add outline import feature; drop Dto naming, map entities at the API boundary

Services now return entities; endpoints (and the agent toolsets) map to
*Response records instead of services building wire DTOs themselves.
Also brings in the outline-import agent, MCP tool, ledger and web dialog
that were already in progress on disk.

src/Novelly.Api/Common/ApiResultExtensions.cs

@@ -2,11 +2,5 @@ namespace Novelly.Api.Common;
 
 public static class ApiResultExtensions
 {
-    /// <summary>
-    /// A missing entity is not exceptional, so lookups return null instead of throwing.
-    /// This is where that null finally becomes an HTTP 404 — the one place the API layer
-    /// needs to know about it.
-    /// </summary>
-    public static IResult ToApiResult<T>(this T? value) where T : class =>
-        value is null ? Results.NotFound() : Results.Ok(value);
+    public static IResult ToApiResult<T>(this T? value) where T : class => value is null ? Results.NotFound() : Results.Ok(value);
 }