Fix HTTP 500 on login: Add ForwardedHeaders middleware for proxy support

- Added UseForwardedHeaders to properly handle X-Forwarded-For and X-Forwarded-Proto
- Fixes anti-forgery token validation when behind nginx proxy
- Resolves HTTP 500 errors on POST requests to login endpoint

LittleShop/Program.cs

@@ -228,6 +228,17 @@ catch (Exception ex)
 
 // Configure the HTTP request pipeline.
 
+// Configure forwarded headers for proxy scenarios (nginx, etc)
+var forwardedHeadersOptions = new Microsoft.AspNetCore.HttpOverrides.ForwardedHeadersOptions
+{
+    ForwardedHeaders = Microsoft.AspNetCore.HttpOverrides.ForwardedHeaders.XForwardedFor |
+                       Microsoft.AspNetCore.HttpOverrides.ForwardedHeaders.XForwardedProto
+};
+// Clear the default known networks/proxies to allow any proxy
+forwardedHeadersOptions.KnownNetworks.Clear();
+forwardedHeadersOptions.KnownProxies.Clear();
+app.UseForwardedHeaders(forwardedHeadersOptions);
+
 // Add CORS early in the pipeline - before authentication
 if (app.Environment.IsDevelopment())
 {