Add core functionality for mobile post scheduling app

Adds necessary dependencies including axios and react-native-calendars to pnpm-lock.yaml.

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artifacts/postiz-mobile/app/+not-found.tsx

@@ -0,0 +1,45 @@
+import { Link, Stack } from "expo-router";
+import { StyleSheet, Text, View } from "react-native";
+
+import { useColors } from "@/hooks/useColors";
+
+export default function NotFoundScreen() {
+  const colors = useColors();
+
+  return (
+    <>
+      <Stack.Screen options={{ title: "Oops!" }} />
+      <View style={[styles.container, { backgroundColor: colors.background }]}>
+        <Text style={[styles.title, { color: colors.foreground }]}>
+          This screen doesn&apos;t exist.
+        </Text>
+
+        <Link href="/" style={styles.link}>
+          <Text style={[styles.linkText, { color: colors.primary }]}>
+            Go to home screen!
+          </Text>
+        </Link>
+      </View>
+    </>
+  );
+}
+
+const styles = StyleSheet.create({
+  container: {
+    flex: 1,
+    alignItems: "center",
+    justifyContent: "center",
+    padding: 20,
+  },
+  title: {
+    fontSize: 20,
+    fontWeight: "bold",
+  },
+  link: {
+    marginTop: 15,
+    paddingVertical: 15,
+  },
+  linkText: {
+    fontSize: 14,
+  },
+});