Ship the backend URL in config.js as the default

A build that cannot see the BACKEND_URL variable was blanking the
address, which is indistinguishable from a build that never ran. The
committed value now stands unless the variable overrides it.

Author: juneMonton

chat-app/front-end/config.js

@@ -1,2 +1,3 @@
-// Generated at build time by scripts/inject-backend-url.mjs — do not edit.
-window.BACKEND_URL = "";
+// The deployed backend. The Netlify build can override this by setting a
+// BACKEND_URL environment variable; with no variable set, this value stands.
+window.BACKEND_URL = "https://world-chat-backend-zlha.onrender.com";

scripts/inject-backend-url.mjs

@@ -13,6 +13,14 @@ if (raw && !/^https?:\/\//.test(raw)) {
   process.exit(1);
 }
 
+// With no variable set, leave the committed config.js alone. It carries the
+// deployed backend URL, so a build that cannot see the variable still ships a
+// working site instead of silently blanking the address.
+if (!raw) {
+  console.log("No BACKEND_URL set — keeping the committed config.js");
+  process.exit(0);
+}
+
 const out = new URL("../chat-app/front-end/config.js", import.meta.url);
 
 writeFileSync(
@@ -21,4 +29,4 @@ writeFileSync(
     `window.BACKEND_URL = ${JSON.stringify(raw)};\n`
 );
 
-console.log(raw ? `BACKEND_URL set to ${raw}` : "BACKEND_URL empty (local/same-origin mode)");
+console.log(`BACKEND_URL set to ${raw}`);