fix(auth): configurable SameSite cookie for cross-origin dev setup

Chrome 89+ schemeful same-site treats http://localhost and https://localhost
as different sites, blocking SameSite=Strict cookies on cross-origin fetch
(e.g. Vite on port 5173, API on port 7221).

Fix: make CookieSameSite configurable per environment in JwtSettings.
- Default: Strict (production)
- appsettings.Development.json: None (allows cross-origin cookie in dev)
- When SameSite=None, Secure is always forced (browser requirement)

Revert the earlier Vite proxy approach in favour of this backend config.
VITE_API_BASE_URL remains a freely configurable URL in .env.local.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

frontend/.env.example

@@ -1,11 +1,6 @@
 # Base URL of the SlpModularCms .NET API.
-#
-# LOCAL DEV (recommended): leave empty and configure the Vite proxy in
-# vite.config.ts. The proxy forwards /api/* to the backend so all requests
-# stay same-origin — required for the SameSite=Strict refresh-token cookie.
-VITE_API_BASE_URL=
-
-# DIRECT (no proxy): point to the backend URL. CORS must allow this origin
-# with credentials, and SameSite may block the cookie on page reload if the
-# schemes differ (e.g. http frontend → https backend).
-# VITE_API_BASE_URL=https://localhost:7221
+# The backend must be running with CORS configured to allow this origin
+# and to send the httpOnly refresh-token cookie (credentials: include).
+# Set CookieSameSite=None in appsettings.Development.json so the cookie
+# is sent cross-origin when the frontend and backend run on different ports.
+VITE_API_BASE_URL=https://localhost:7221

frontend/src/lib/config.ts

@@ -6,8 +6,7 @@ import { z } from 'zod';
  * once and only warns in development — production trusts the build-time env.
  */
 const configSchema = z.object({
-    // Empty string = use Vite proxy (same-origin); a full URL = direct mode.
-    apiBaseUrl: z.union([z.literal(''), z.string().url()]),
+    apiBaseUrl: z.string().url(),
 });
 
 export type AppConfig = z.infer<typeof configSchema>;

frontend/vite.config.ts

@@ -14,17 +14,6 @@ export default defineConfig({
     },
     server: {
         port: 5173,
-        proxy: {
-            // Route all /api calls through the Vite dev server so the browser
-            // sees a single origin. Without this the refreshToken cookie
-            // (SameSite=Strict) is not sent from http://localhost to
-            // https://localhost (different scheme = cross-site in Chrome 89+).
-            '/api': {
-                target: 'https://localhost:7221',
-                changeOrigin: true,
-                secure: false, // allow self-signed dev cert
-            },
-        },
     },
     test: {
         globals: true,

src/SlpModularCms.Api/appsettings.Development.json

@@ -13,7 +13,8 @@
     "Issuer": "SlpModularCms",
     "Audience": "SlpModularCmsPortal",
     "ExpiryMinutes": 60,
-    "RefreshTokenExpiryDays": 7
+    "RefreshTokenExpiryDays": 7,
+    "CookieSameSite": "None"
   },
   "Availability": {
     "CircuitBreakerSeconds": 30,

src/SlpModularCms.Core/Identity/Models/JwtSettings.cs

@@ -10,4 +10,10 @@ public class JwtSettings
     public string Audience { get; set; } = string.Empty;
     public int ExpiryMinutes { get; set; } = 60;
     public int RefreshTokenExpiryDays { get; set; } = 7;
+    /// <summary>
+    /// SameSite-modus voor de refreshToken cookie: Strict | Lax | None.
+    /// Gebruik None in ontwikkelomgevingen waar frontend en backend
+    /// op verschillende poorten draaien (vereist Secure=true).
+    /// </summary>
+    public string CookieSameSite { get; set; } = "Strict";
 }

src/SlpModularCms.Modules.Identity/Controllers/AuthController.cs

@@ -2,6 +2,7 @@ using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.RateLimiting;
+using Microsoft.Extensions.Options;
 using SlpModularCms.Core.Identity.Models;
 using SlpModularCms.Core.Identity.Services;
 
@@ -12,10 +13,12 @@ namespace SlpModularCms.Modules.Identity.Controllers;
 public class AuthController : ControllerBase
 {
     private readonly IAuthService _authService;
+    private readonly JwtSettings _jwtSettings;
 
-    public AuthController(IAuthService authService)
+    public AuthController(IAuthService authService, IOptions<JwtSettings> jwtSettings)
     {
         _authService = authService;
+        _jwtSettings = jwtSettings.Value;
     }
 
     [HttpPost("login")]
@@ -65,11 +68,15 @@ public class AuthController : ControllerBase
 
     private CookieOptions GetCookieOptions()
     {
+        var sameSite = Enum.TryParse<SameSiteMode>(_jwtSettings.CookieSameSite, ignoreCase: true, out var parsed)
+            ? parsed
+            : SameSiteMode.Strict;
+
         return new CookieOptions
         {
             HttpOnly = true,
-            Secure = Request.IsHttps,
-            SameSite = SameSiteMode.Strict,
+            Secure = Request.IsHttps || sameSite == SameSiteMode.None,
+            SameSite = sameSite,
             Path = "/api/v1/auth",
             Expires = DateTimeOffset.UtcNow.AddDays(7)
         };