feat(api): #288 wrap raw VMs, nullable-honest DTOs, search pageNum

24 #nullable enable flips across ErsatzTV.Core/Api; Collection/Schedule/
SmartCollection/Resolution VMs wrapped in ResponseModels (Version now
header-only, SPA-verified); pageNum threaded into GET /api/search.

Refs #288 #197

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

ErsatzTV/Controllers/Api/ResolutionController.cs

@@ -14,11 +14,19 @@ namespace ErsatzTV.Controllers.Api;
 [EndpointGroupName("general")]
 public class ResolutionController(IMediator mediator) : ControllerBase
 {
-    [HttpGet("/api/ffmpeg/resolution/by-name/{name}", Name="GetResolutionByName")]
-    public async Task<ActionResult<ResolutionViewModel>> GetResolutionByName(string name, CancellationToken cancellationToken)
+    [HttpGet("/api/ffmpeg/resolution/by-name/{name}", Name = "GetResolutionByName")]
+    [Tags("Settings")]
+    [EndpointSummary("Get a resolution by name")]
+    [ProducesResponseType(typeof(ResolutionResponseModel), StatusCodes.Status200OK)]
+    [ProducesResponseType(typeof(ProblemDetails), StatusCodes.Status404NotFound)]
+    public async Task<ActionResult<ResolutionResponseModel>> GetResolutionByName(
+        string name,
+        CancellationToken cancellationToken)
     {
         Option<ResolutionViewModel> result = await mediator.Send(new GetResolutionByName(name), cancellationToken);
-        return result.Match<ActionResult<ResolutionViewModel>>(i => Ok(i), () => NotFound());
+        return result.Match<ActionResult<ResolutionResponseModel>>(
+            i => Ok(ProjectToResponseModel(i)),
+            () => NotFound());
     }
 
     [HttpGet("/api/settings/resolutions", Name = "GetResolutions")]