android: enable offline sync and hide theme toggle in Tauri app

Detect Tauri via __TAURI__ in pwaStore so the offline recipe sync,
image caching, and auto-sync activate in the Android shell.

src/lib/stores/pwa.svelte.ts

@@ -30,10 +30,13 @@ function createPWAStore() {
 
 	let autoSyncInterval: ReturnType<typeof setInterval> | null = null;
 
-	// Check if running as installed PWA (standalone mode)
+	// Check if running as installed PWA or Tauri app
 	function checkStandaloneMode(): boolean {
 		if (!browser) return false;
 
+		// Check Tauri Android shell
+		if ('__TAURI__' in window) return true;
+
 		// Check display-mode media query (works on most browsers)
 		const standaloneQuery = window.matchMedia('(display-mode: standalone)');
 		if (standaloneQuery.matches) return true;