Initial commit

src/PowderCoating.Web/Controllers/ThemeController.cs

@@ -0,0 +1,25 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace PowderCoating.Web.Controllers;
+
+/// <summary>
+/// Sets the surface theme preference cookie server-side so it survives page navigation reliably.
+/// Client-side document.cookie writes can silently fail on some browser/HTTPS configurations.
+/// </summary>
+public class ThemeController : Controller
+{
+    [HttpPost]
+    [IgnoreAntiforgeryToken]
+    public IActionResult Set([FromForm] string surface)
+    {
+        var value = surface == "ink" ? "ink" : "paper";
+        Response.Cookies.Append("pcl_surface", value, new CookieOptions
+        {
+            Path = "/",
+            MaxAge = TimeSpan.FromDays(365),
+            SameSite = SameSiteMode.Lax,
+            HttpOnly = false
+        });
+        return Ok();
+    }
+}