Fix login button and improve CORS

- Fixed login URL from /auth/steam to /api/auth/steam
- Updated all Steam login buttons to custom green design with 'Login to Steam' text
- Enhanced CORS configuration with explicit preflight handling
- Added Steam image proxy endpoint for CORS-free image loading
- Improved environment variable management with .env.local support
- Added ENV_SETUP.md guide for environment configuration

index.js

@@ -91,9 +91,19 @@ const registerPlugins = async (fastify) => {
       }
     },
     credentials: true,
-    methods: ["GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS"],
-    allowedHeaders: ["Content-Type", "Authorization", "Cookie"],
-    exposedHeaders: ["Set-Cookie"],
+    methods: ["GET", "POST", "PUT", "PATCH", "DELETE", "OPTIONS", "HEAD"],
+    allowedHeaders: [
+      "Content-Type",
+      "Authorization",
+      "Cookie",
+      "X-Requested-With",
+      "Accept",
+    ],
+    exposedHeaders: ["Set-Cookie", "Content-Type"],
+    preflight: true,
+    preflightContinue: false,
+    optionsSuccessStatus: 204,
+    maxAge: 86400, // Cache preflight requests for 24 hours
   });
 
   // Security headers