feat(packaging): bundle app icon + Linux desktop entry; wire into AUR package

- release tarballs now ship podtui.png (assets/App Icon/App Icon.png, 512px)
  on every platform; Linux tarballs additionally carry podtui.desktop
  (Terminal=true so launchers open the TUI in a terminal)
- AUR PKGBUILD installs both: icon to hicolor 512x512, entry to applications/
- build.ts bundles the icon/desktop into dist before tarballing

packaging/aur/PKGBUILD

@@ -51,5 +51,13 @@ package() {
 	install -Dm644 "${srcdir}/${libdir}/libcavacore.so" "${pkgdir}/usr/lib/podtui/libcavacore.so"
 	install -Dm644 "${srcdir}/${libdir}/libopentui.so" "${pkgdir}/usr/lib/podtui/libopentui.so"
 	ln -s /usr/lib/podtui/podtui "${pkgdir}/usr/bin/podtui"
+
+	# App icon + desktop entry ship inside the release tarball; Terminal=true
+	# makes launchers drop the TUI into a terminal window.
+	install -Dm644 "${srcdir}/${libdir}/podtui.png" \
+		"${pkgdir}/usr/share/icons/hicolor/512x512/apps/podtui.png"
+	install -Dm644 "${srcdir}/${libdir}/podtui.desktop" \
+		"${pkgdir}/usr/share/applications/podtui.desktop"
+
 	install -Dm644 "${srcdir}/LICENSE" "${pkgdir}/usr/share/licenses/${pkgname}/LICENSE"
 }