fix: move PyodideWebView into Import tab; fix micropip blob URL error

Layout fix: WebView as a sibling in the root layout breaks flex geometry even
with position:absolute. Moving it inside the Import tab screen (which Expo Router
keeps mounted after first visit) eliminates the issue entirely and restores the
original simple root layout.

micropip fix: blob: URLs are not a recognised scheme in micropip — they are parsed
as package requirement strings, producing InvalidRequirement. Write the wheel bytes
to Pyodide's Emscripten FS (/tmp/bincio.whl) and install via emfs:/// instead.

mobile/app/_layout.tsx

@@ -1,24 +1,13 @@
 import { Stack } from 'expo-router';
 import { SQLiteProvider } from 'expo-sqlite';
 import { StatusBar } from 'expo-status-bar';
-import { StyleSheet, View } from 'react-native';
 import { migrateDb } from '@/db';
-import { PyodideWebView } from '@/extraction/PyodideWebView';
 
 export default function RootLayout() {
   return (
-    <View style={styles.root}>
-      {/* Hidden WebView: starts loading Pyodide immediately so the runtime
-          is warm by the time the user opens the Import tab. */}
-      <PyodideWebView />
-      <SQLiteProvider databaseName="bincio.db" onInit={migrateDb}>
-        <StatusBar style="light" />
-        <Stack screenOptions={{ headerShown: false }} />
-      </SQLiteProvider>
-    </View>
+    <SQLiteProvider databaseName="bincio.db" onInit={migrateDb}>
+      <StatusBar style="light" />
+      <Stack screenOptions={{ headerShown: false }} />
+    </SQLiteProvider>
   );
 }
-
-const styles = StyleSheet.create({
-  root: { flex: 1 },
-});