fix: update website version to 0.4.0-alpha (#86)

The website was displaying an outdated version (0.3.0-alpha) instead of
the current version (0.4.0-alpha) from src/vocalinux/version.py.

Updated version references in:
- web/src/app/page.tsx (header badge)
- web/src/app/layout.tsx (structured data)

web/src/app/layout.tsx

@@ -116,7 +116,7 @@ export default function RootLayout({
       "priceCurrency": "USD"
     },
     "description": "Free, open-source voice dictation for Linux. 100% offline with Whisper AI and VOSK. Works with X11 and Wayland.",
-    "softwareVersion": "0.3.0-alpha",
+    "softwareVersion": "0.4.0-alpha",
     "author": {
       "@type": "Person",
       "name": "Jatin K Malik",

web/src/app/page.tsx

@@ -204,7 +204,7 @@ export default function HomePage() {
             />
             <span className="font-bold text-lg sm:text-xl">Vocalinux</span>
             <span className="hidden sm:inline-block text-xs bg-gradient-to-r from-primary/20 to-green-500/20 text-primary border border-primary/30 px-2.5 py-1 rounded-full font-semibold shadow-sm shadow-primary/20">
-              v0.3.0 Alpha
+              v0.4.0 Alpha
             </span>
           </Link>