fix(mobile): correct asset logo path depth and add expo-router app/ routes for web support

- Fix fatal crash: require('../../../assets/logo.png') in LoginScreen and
  WelcomeScreen resolved 3 levels above mobile/src/screens/ — outside the
  mobile/ directory. Changed to ../../assets/logo.png which correctly
  resolves to the existing mobile/assets/logo.png.
- Add expo-router app/ directory (root cause of missing welcome screen and
  web support): app/_layout.tsx, (auth)/, (tabs)/ with all route files
- Add WelcomeScreen.tsx: branded intro screen with feature highlights
- Update LoginScreen/WelcomeScreen to use useRouter() (expo-router style)
- Add react-native-web ~0.20.0 and react-dom 19.2.4 for web channel
- Add expo-device ~7.0.3 (was imported but missing from package.json)
- Remove android.googleServicesFile from app.json (file is gitignored;
  README documents how to restore it for Android FCM builds)
- Add web.bundler: metro and web.output: single to app.json
- Fix aria-hidden to explicit boolean value in WelcomeScreen

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

mobile/src/screens/LoginScreen.tsx

@@ -6,7 +6,7 @@
  * AuthContext stores the API token and navigates to the main app.
  */
 
-import type { NativeStackNavigationProp } from "@react-navigation/native-stack";
+import { useRouter } from "expo-router";
 import React, { useState } from "react";
 import {
   ActivityIndicator,
@@ -21,14 +21,10 @@ import {
   View,
 } from "react-native";
 import { useAuth } from "../context/AuthContext";
-import type { AuthStackParamList } from "./WelcomeScreen";
 
-type LoginScreenProps = {
-  navigation: NativeStackNavigationProp<AuthStackParamList, "Login">;
-};
-
-export default function LoginScreen({ navigation }: LoginScreenProps) {
+export default function LoginScreen() {
   const { signIn } = useAuth();
+  const router = useRouter();
   const [serverUrl, setServerUrl] = useState("");
   const [loading, setLoading] = useState(false);
 
@@ -62,7 +58,7 @@ export default function LoginScreen({ navigation }: LoginScreenProps) {
       <View style={styles.card}>
         <View style={styles.logoContainer}>
           <Image
-            source={require("../../../assets/logo.png")}
+            source={require("../../assets/logo.png")}
             style={styles.logoImage}
             resizeMode="contain"
             accessibilityLabel="DocuElevate logo"
@@ -105,7 +101,7 @@ export default function LoginScreen({ navigation }: LoginScreenProps) {
         </Text>
 
         <Pressable
-          onPress={() => navigation.navigate("Welcome")}
+          onPress={() => router.back()}
           accessibilityRole="button"
           accessibilityLabel="Back to welcome screen"
           style={styles.backLink}

mobile/src/screens/WelcomeScreen.tsx

@@ -5,7 +5,7 @@
  * and a "Get Started" button that navigates to the LoginScreen.
  */
 
-import type { NativeStackNavigationProp } from "@react-navigation/native-stack";
+import { useRouter } from "expo-router";
 import React from "react";
 import {
   Image,
@@ -17,15 +17,6 @@ import {
   View,
 } from "react-native";
 
-export type AuthStackParamList = {
-  Welcome: undefined;
-  Login: undefined;
-};
-
-type WelcomeScreenProps = {
-  navigation: NativeStackNavigationProp<AuthStackParamList, "Welcome">;
-};
-
 const FEATURES: { icon: string; title: string; description: string }[] = [
   {
     icon: "🔍",
@@ -44,7 +35,8 @@ const FEATURES: { icon: string; title: string; description: string }[] = [
   },
 ];
 
-export default function WelcomeScreen({ navigation }: WelcomeScreenProps) {
+export default function WelcomeScreen() {
+  const router = useRouter();
   return (
     <SafeAreaView style={styles.safe}>
       <ScrollView
@@ -55,7 +47,7 @@ export default function WelcomeScreen({ navigation }: WelcomeScreenProps) {
         <View style={styles.hero}>
           <View style={styles.logoContainer}>
             <Image
-              source={require("../../../assets/logo.png")}
+              source={require("../../assets/logo.png")}
               style={styles.logoImage}
               resizeMode="contain"
               accessibilityLabel="DocuElevate logo"
@@ -73,7 +65,7 @@ export default function WelcomeScreen({ navigation }: WelcomeScreenProps) {
         <View style={styles.features}>
           {FEATURES.map((feature) => (
             <View key={feature.title} style={styles.featureRow}>
-              <Text style={styles.featureIcon} aria-hidden>{feature.icon}</Text>
+              <Text style={styles.featureIcon} aria-hidden={true}>{feature.icon}</Text>
               <View style={styles.featureText}>
                 <Text style={styles.featureTitle}>{feature.title}</Text>
                 <Text style={styles.featureDescription}>{feature.description}</Text>
@@ -85,7 +77,7 @@ export default function WelcomeScreen({ navigation }: WelcomeScreenProps) {
         {/* CTA */}
         <Pressable
           style={({ pressed }) => [styles.button, pressed && styles.buttonPressed]}
-          onPress={() => navigation.navigate("Login")}
+          onPress={() => router.push("/(auth)/login")}
           accessibilityRole="button"
           accessibilityLabel="Get started — connect to your DocuElevate server"
         >