[backend/razor] Show login button when displaying public preview disabled error page

Iceshrimp.Backend/Controllers/Razor/RedirectController.cs

@@ -30,8 +30,7 @@ public class RedirectController(IOptionsSnapshot<Config.SecuritySection> config,
 	{
 		var localUser = HttpContext.GetUser();
 		if (config.Value.PublicPreview == Enums.PublicPreview.Lockdown && localUser == null)
-			throw GracefulException.Forbidden("Public preview is disabled on this instance.",
-			                                  "The instance administrator has intentionally disabled this feature for privacy reasons.");
+			throw new PublicPreviewDisabledException();
 
 		var user = await db.Users.IncludeCommonProperties().FirstOrDefaultAsync(p => p.Id == id) ??
 		           throw GracefulException.NotFound("User not found");

Iceshrimp.Backend/Core/Extensions/ServiceExtensions.cs

@@ -290,7 +290,7 @@ public static class ServiceExtensions
 			{
 				context.HttpContext.Response.StatusCode  = 429;
 				context.HttpContext.Response.ContentType = "application/json";
-				var res = new ErrorResponse
+				var res = new ErrorResponse(new Exception())
 				{
 					Error      = "Too Many Requests",
 					StatusCode = 429,

Iceshrimp.Backend/Core/Middleware/ErrorHandlerMiddleware.cs

@@ -92,7 +92,7 @@ public class ErrorHandlerMiddleware(
 				}
 				else
 				{
-					var error = new ErrorResponse
+					var error = new ErrorResponse(e)
 					{
 						StatusCode = ctx.Response.StatusCode,
 						Error      = verbosity >= ExceptionVerbosity.Basic ? ce.Error : ce.StatusCode.ToString(),
@@ -121,7 +121,7 @@ public class ErrorHandlerMiddleware(
 				ctx.Response.StatusCode        = 500;
 				ctx.Response.Headers.RequestId = ctx.TraceIdentifier;
 
-				var error = new ErrorResponse
+				var error = new ErrorResponse(e)
 				{
 					StatusCode = 500,
 					Error      = "Internal Server Error",
@@ -277,6 +277,10 @@ public class InstanceBlockedException(string uri, string? host = null)
 	public string Uri => uri;
 }
 
+public class PublicPreviewDisabledException()
+	: GracefulException(HttpStatusCode.Forbidden, "Public preview is disabled on this instance.",
+	                    "The instance administrator has intentionally disabled this feature for privacy reasons.");
+
 public class ValidationException(
 	HttpStatusCode statusCode,
 	string error,

Iceshrimp.Backend/Pages/Note.cshtml.cs

@@ -41,8 +41,7 @@ public class NoteModel(
 			return Partial("Shared/FrontendSPA");
 
 		if (security.Value.PublicPreview == Enums.PublicPreview.Lockdown)
-			throw GracefulException.Forbidden("Public preview is disabled on this instance.",
-			                                  "The instance administrator has intentionally disabled this feature for privacy reasons.");
+			throw new PublicPreviewDisabledException();
 
 		InstanceName = await meta.Get(MetaEntity.InstanceName) ?? InstanceName;
 

Iceshrimp.Backend/Pages/Shared/ErrorPage.cshtml

@@ -1,5 +1,6 @@
 @page
 @using Iceshrimp.Backend.Core.Configuration
+@using Iceshrimp.Backend.Core.Middleware
 @using Microsoft.Extensions.Options
 @model ErrorPageModel
 @inject IOptions<Config.InstanceSection>         Instance
@@ -60,6 +61,12 @@
 </p>
 <footer>
     <strong>Iceshrimp.NET</strong> v@(Instance.Value.Version)
+    @if (Model.Error.Exception is PublicPreviewDisabledException)
+    {
+        <span class="float-right">
+            <a href="/login?rd=@(Request.Path.ToUriComponent())">Login</a>
+        </span>
+    }
 </footer>
 </body>
 </html>

Iceshrimp.Backend/Pages/Shared/_Layout.cshtml

@@ -20,12 +20,12 @@
 @await RenderSectionAsync("scripts", false)
 <footer>
     <strong>Iceshrimp.NET</strong> v@(Instance.Value.Version)
-    <span class="float-right">
-        @if (!Context.ShouldHideFooter())
-        {
+    @if (!Context.ShouldHideFooter())
+    {
+        <span class="float-right">
             <a href="/login?rd=@(Context.Request.Path.ToUriComponent())">Login</a>
-        }
-    </span>
+        </span>
+    }
 </footer>
 </body>
 </html>

Iceshrimp.Backend/Pages/User.cshtml.cs

@@ -39,8 +39,7 @@ public class UserModel(
 			return Partial("Shared/FrontendSPA");
 
 		if (security.Value.PublicPreview == Enums.PublicPreview.Lockdown)
-			throw GracefulException.Forbidden("Public preview is disabled on this instance.",
-			                                  "The instance administrator has intentionally disabled this feature for privacy reasons.");
+			throw new PublicPreviewDisabledException();
 
 		InstanceName = await meta.Get(MetaEntity.InstanceName) ?? InstanceName;
 

Iceshrimp.Shared/Schemas/Web/ErrorResponse.cs

@@ -5,7 +5,7 @@ using JI = System.Text.Json.Serialization.JsonIgnoreAttribute;
 namespace Iceshrimp.Shared.Schemas.Web;
 
 [XmlRoot("Error")]
-public class ErrorResponse
+public class ErrorResponse(Exception exception)
 {
 	[XmlElement("Status")] public required int    StatusCode { get; set; }
 	[XmlElement("Error")]  public required string Error      { get; set; }
@@ -37,6 +37,8 @@ public class ErrorResponse
 	public string? Source { get; set; }
 
 	[XmlElement("RequestId")] public required string RequestId { get; set; }
+
+	[JI] [XmlIgnore] public Exception Exception => exception;
 }
 
 public class XmlValidationError