Record into a Jellyfin library by default; configurable recording location

When no custom directory is set, recordings go to an "SRF Recordings" folder
in the chosen library, or the first TV Shows library, so they show up without
adding a library by hand. The settings page gets a library picker, a check
that the directory is writable, and help for sandboxed systemd services.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Jellyfin.Plugin.SRFPlay/Controllers/RecordingController.cs

@@ -6,6 +6,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using Jellyfin.Plugin.SRFPlay.Api.Models;
 using Jellyfin.Plugin.SRFPlay.Services.Interfaces;
+using MediaBrowser.Common.Api;
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
@@ -238,4 +239,16 @@ public class RecordingController : ControllerBase
     {
         return _recordingService.DeleteRecording(id, deleteFile) ? Ok() : NotFound();
     }
+
+    /// <summary>
+    /// Shows where recordings will be written and whether the server can write there.
+    /// </summary>
+    /// <returns>The resolved output directory and write-test result.</returns>
+    [HttpGet("OutputInfo")]
+    [Authorize(Policy = Policies.RequiresElevation)]
+    [ProducesResponseType(StatusCodes.Status200OK)]
+    public ActionResult<RecordingOutputInfo> GetOutputInfo()
+    {
+        return Ok(_recordingService.GetOutputInfo());
+    }
 }