fix: Improve MESSAGE PASSWORD contrast and add global Buffer polyfill shim

src/App.tsx

@@ -621,7 +621,7 @@ function App() {
                         readOnly={isReadOnly}
                       />
                     </div>
-                    <p className="text-[10px] text-slate-800 mt-1">
+                    <p className="text-[10px] text-slate-300 mt-1">
                       {encryptionMode === 'krux'
                         ? 'Required passphrase for Krux encryption'
                         : 'Symmetric encryption password (SKESK)'}

src/main.tsx

@@ -1,3 +1,5 @@
+import './polyfills';
+
 // Suppress OpenPGP.js AES cipher warnings
 const originalWarn = console.warn;
 const originalError = console.error;

src/polyfills.ts

@@ -0,0 +1,7 @@
+import { Buffer } from 'buffer';
+
+// Make Buffer available globally for libraries that expect it
+if (typeof window !== 'undefined') {
+  (window as any).Buffer = Buffer;
+  (window as any).global = window;
+}