Address utf8 support when uploading JavaScript application

OFW PR 4364 by bekindpleaserewind

CHANGELOG.md

@@ -9,6 +9,7 @@
 * OFW PR 4362: NFC: Fix BusFault in Write to Initial Card (by @akrylysov)
 * Apps: Build tag (**27mar2026**) - **Check out more Apps updates and fixes by following** [this link](https://github.com/xMasterX/all-the-plugins/commits/dev)
 ## Other changes
+* OFW PR 4364: JS: Address utf8 support when uploading JavaScript application (by @bekindpleaserewind)
 * Display: Extend lcd contrast range to full ST756x 6-bit range (by @ShaTie) (reduced to -10 to +18 to avoid fully unreadable state)
 <br><br>
 #### Known NFC post-refactor regressions list: 

applications/system/js_app/packages/fz-sdk/sdk.js

@@ -153,10 +153,11 @@ async function upload(config) {
     port.write(`storage remove ${config.output}\x0d`);
     port.drain();
     await waitFor(">: ", 1000);
-    port.write(`storage write_chunk ${config.output} ${appFile.length}\x0d`);
+    const appFileBuffer = Buffer.from(appFile, "utf8");
+    port.write(`storage write_chunk ${config.output} ${appFileBuffer.length}\x0d`);
     await waitFor("Ready", 1000);
-    port.write(appFile);
-    port.drain();
+    port.write(appFileBuffer);
+    await new Promise(resolve => port.drain(resolve));
     await waitFor(">: ", 1000);
 
     console.log("Launching application");