fix(mobile): migrate to Expo SDK 54, replace NativeWind with StyleSheet

- Update package.json to Expo ~54.0.35, expo-router ~6.0.24, RN 0.81.5
- Remove NativeWind/Tailwind dependencies
- Fix babel.config.js: presets babel-preset-expo only
- Rewrite all screens with StyleSheet.create (no className)
- Add lucide-react-native + react-native-svg
- Export design tokens C from _layout.tsx for shared usage
- Install node_modules (702 packages)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

memento-mobile/app/(auth)/login.tsx

@@ -1,15 +1,11 @@
 import { useState } from 'react'
 import {
-  View,
-  Text,
-  TextInput,
-  TouchableOpacity,
-  KeyboardAvoidingView,
-  Platform,
-  ActivityIndicator,
-  Alert,
+  View, Text, TextInput, TouchableOpacity,
+  KeyboardAvoidingView, Platform, ActivityIndicator,
+  Alert, StyleSheet,
 } from 'react-native'
 import { useAuthStore } from '@/lib/store'
+import { C } from '../_layout'
 
 export default function LoginScreen() {
   const [email, setEmail] = useState('')
@@ -30,69 +26,56 @@ export default function LoginScreen() {
   }
 
   return (
-    <KeyboardAvoidingView
-      behavior={Platform.OS === 'ios' ? 'padding' : 'height'}
-      className="flex-1 bg-paper"
-    >
-      <View className="flex-1 justify-center px-8">
-        {/* Logo */}
-        <View className="mb-12 items-center">
-          <Text className="text-4xl font-serif text-ink italic tracking-tight">Momento</Text>
-          <Text className="text-sm text-concrete mt-1">Votre espace de connaissance</Text>
+    <KeyboardAvoidingView behavior={Platform.OS === 'ios' ? 'padding' : 'height'} style={s.container}>
+      <View style={s.inner}>
+        <View style={s.logoBlock}>
+          <Text style={s.logo}>Momento</Text>
+          <Text style={s.tagline}>Votre espace de connaissance</Text>
         </View>
 
-        {/* Form */}
-        <View className="space-y-3">
-          <View>
-            <Text className="text-[11px] font-semibold uppercase tracking-widest text-concrete mb-1.5">
-              Email
-            </Text>
-            <TextInput
-              value={email}
-              onChangeText={setEmail}
-              placeholder="vous@exemple.com"
-              autoCapitalize="none"
-              keyboardType="email-address"
-              autoComplete="email"
-              className="w-full border border-border rounded-xl px-4 py-3 text-ink text-[15px] bg-white"
-              placeholderTextColor="#8A8A82"
-            />
-          </View>
-
-          <View>
-            <Text className="text-[11px] font-semibold uppercase tracking-widest text-concrete mb-1.5">
-              Mot de passe
-            </Text>
-            <TextInput
-              value={password}
-              onChangeText={setPassword}
-              placeholder="••••••••"
-              secureTextEntry
-              autoComplete="password"
-              className="w-full border border-border rounded-xl px-4 py-3 text-ink text-[15px] bg-white"
-              placeholderTextColor="#8A8A82"
-              onSubmitEditing={handleLogin}
-            />
-          </View>
-
+        <View style={s.form}>
+          <Text style={s.label}>Email</Text>
+          <TextInput
+            value={email} onChangeText={setEmail}
+            placeholder="vous@exemple.com" autoCapitalize="none"
+            keyboardType="email-address" autoComplete="email"
+            style={s.input} placeholderTextColor={C.concrete}
+          />
+          <Text style={[s.label, { marginTop: 16 }]}>Mot de passe</Text>
+          <TextInput
+            value={password} onChangeText={setPassword}
+            placeholder="••••••••" secureTextEntry
+            autoComplete="password" style={s.input}
+            placeholderTextColor={C.concrete} onSubmitEditing={handleLogin}
+          />
           <TouchableOpacity
             onPress={handleLogin}
             disabled={loading || !email || !password}
-            className="mt-4 bg-ink rounded-xl py-3.5 items-center active:opacity-80"
-            style={{ opacity: loading || !email || !password ? 0.5 : 1 }}
+            style={[s.btn, (loading || !email || !password) && s.btnDisabled]}
           >
-            {loading ? (
-              <ActivityIndicator color="white" size="small" />
-            ) : (
-              <Text className="text-paper font-semibold text-[15px]">Se connecter</Text>
-            )}
+            {loading
+              ? <ActivityIndicator color={C.white} size="small" />
+              : <Text style={s.btnText}>Se connecter</Text>}
           </TouchableOpacity>
         </View>
 
-        <Text className="text-center text-[12px] text-concrete mt-8">
-          memento-note.com
-        </Text>
+        <Text style={s.footer}>memento-note.com</Text>
       </View>
     </KeyboardAvoidingView>
   )
 }
+
+const s = StyleSheet.create({
+  container: { flex: 1, backgroundColor: C.paper },
+  inner: { flex: 1, justifyContent: 'center', paddingHorizontal: 32 },
+  logoBlock: { marginBottom: 48, alignItems: 'center' },
+  logo: { fontSize: 36, fontStyle: 'italic', color: C.ink, fontWeight: '600' },
+  tagline: { fontSize: 14, color: C.concrete, marginTop: 4 },
+  form: {},
+  label: { fontSize: 11, fontWeight: '700', letterSpacing: 1.5, textTransform: 'uppercase', color: C.concrete, marginBottom: 6 },
+  input: { borderWidth: 1, borderColor: C.border, borderRadius: 12, paddingHorizontal: 16, paddingVertical: 12, fontSize: 15, color: C.ink, backgroundColor: C.white },
+  btn: { marginTop: 24, backgroundColor: C.ink, borderRadius: 12, paddingVertical: 14, alignItems: 'center' },
+  btnDisabled: { opacity: 0.5 },
+  btnText: { color: C.white, fontWeight: '600', fontSize: 15 },
+  footer: { textAlign: 'center', fontSize: 12, color: C.concrete, marginTop: 32 },
+})