[backend/razor] Add instance icon and banner to home page

Iceshrimp.Backend/Pages/Index.cshtml

@@ -3,8 +3,6 @@
 @* ReSharper disable Html.PathError *@
 @{
     ViewData["title"] = $"Home - {Model.InstanceName}";
-
-    //TODO: logo / banner & favicon
 }
 
 @section head
@@ -16,11 +14,23 @@
 }
 
 <div class="header">
-    <h1>@Model.InstanceName</h1>
+    <span>
+        @if (Model.IconUrl != null)
+        {
+            <img class="icon" src="@Model.IconUrl" alt="icon"/>
+        }
+        <h1>@Model.InstanceName</h1>
+    </span>
     <div class="wordmark">
         <img src="~/_content/Iceshrimp.Assets.Branding/welcome-logo.svg" alt="Iceshrimp"/>
     </div>
 </div>
+
+@if (Model.BannerUrl != null)
+{
+    <img class="banner" src="@Model.BannerUrl" alt="banner"/>
+}
+
 <p>@Model.InstanceDescription</p>
 
 @if (Model.Rules.Count != 0)

Iceshrimp.Backend/Pages/Index.cshtml.cs

@@ -13,6 +13,8 @@ public class IndexModel(MetaService meta, InstanceService instance, IOptionsSnap
 	public string?    ContactEmail;
 	public string     InstanceDescription = null!;
 	public string     InstanceName        = null!;
+	public string?    IconUrl;
+	public string?    BannerUrl;
 	public List<Rule> Rules = [];
 
 	public async Task<IActionResult> OnGet()
@@ -32,6 +34,8 @@ public class IndexModel(MetaService meta, InstanceService instance, IOptionsSnap
 			instanceDescription ?? "This Iceshrimp.NET instance does not appear to have a description";
 		ContactEmail = contactEmail;
 
+		(IconUrl, BannerUrl) = await instance.GetInstanceImageAsync();
+
 		Rules = await instance.GetRulesAsync();
 
 		return Page();

Iceshrimp.Backend/Pages/Index.cshtml.css

@@ -8,12 +8,34 @@
     gap: 0 12px;
 }
 
-.header>h1 {
+.header span {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.5rem;
+}
+
+.header h1 {
     margin: 0;
 }
 
+.header .icon {
+    width: 3rem;
+    height: 3rem;
+    border-radius: 8px;
+    line-height: 1;
+}
+
 .header>.wordmark {
     width: 160px;
     line-height: 0;
     padding-bottom: 4px;
+}
+
+.banner {
+    display: block;
+    width: 100%;
+    height: auto;
+    object-fit: cover;
+    aspect-ratio: 21/9;
+    border-radius: 1rem;
 }