Add support page, admin features, and auth hardening.

Rename public affiliate route to /support with localized nav labels, and include affiliate/social/wallpaper admin, 2FA login, and related site updates.

Co-authored-by: Cursor <cursoragent@cursor.com>

Views/admin/wallpaper.cshtml

@@ -0,0 +1,37 @@
+@{
+    ViewBag.Title = "wallpaper";
+    Layout = "~/Views/Shared/_AdminLayout.cshtml";
+}
+
+<h2 class="text-white mt-3 mb-3">Wallpaper</h2>
+<p class="text-white-50">This image is used as the background on every public page.</p>
+@if (TempData["ok"] != null)
+{<div class="alert alert-success">@TempData["ok"]</div>}
+
+<div class="mb-4">
+    <label class="text-white d-block mb-2">Current wallpaper</label>
+    <img src="@ViewBag.CurrentWallpaper" style="max-width:100%;max-height:300px;border-radius:8px;border:1px solid #444;" />
+</div>
+
+@using (Html.BeginForm("Wallpaper", "admin", FormMethod.Post, new { enctype = "multipart/form-data" }))
+{
+    @Html.AntiForgeryToken()
+
+    <div class="mb-3">
+        <label class="text-white">New wallpaper image</label>
+        <img id="wallpaperPreview" style="display:none;max-width:100%;max-height:300px;border-radius:8px;" class="mb-2 d-block" />
+        <input id="wallpaperFile" type="file" name="wallpaperFile" class="form-control bg-dark text-white" accept="image/*" />
+        <button type="button" class="btn btn-outline-light btn-sm mt-2" onclick="PasteImageModal.open('#wallpaperFile', '#wallpaperPreview')">
+            <i class="fa-solid fa-paste me-1"></i>Paste image
+        </button>
+        <small class="text-muted d-block mt-1">PNG, JPG, WEBP or GIF.</small>
+    </div>
+
+    <button class="btn btn-success">Upload New Wallpaper</button>
+}
+
+@using (Html.BeginForm("WallpaperReset", "admin", FormMethod.Post, new { onsubmit = "return confirm('Reset wallpaper to the default image?');" }))
+{
+    @Html.AntiForgeryToken()
+    <button type="submit" class="btn btn-secondary mt-2">Reset to Default</button>
+}