feat: App mobile Expo + API mobile dédiée

memento-mobile/ (Expo + React Native + expo-router):
- Auth: login email/password → Bearer token (expo-secure-store)
- Layout: guard auth → redirect /(auth)/login ou /(tabs)/home
- Tabs: Accueil, Carnets, Recherche, Profil
- Screens: login, home (recent notes + quick actions), notebooks list,
  note viewer (WebView HTML), search (texte), notebook detail, profile
- Design: tokens brand-accent (#A47148), ink, concrete, paper, border
- lib/config.ts: API_URL dev/prod configurable
- lib/api.ts: apiFetch avec Bearer token automatique
- lib/store.ts: Zustand auth store (login/logout/restore)

memento-note/ (API mobile dédiée):
- lib/mobile-auth.ts: createMobileToken / verifyMobileToken (HMAC-SHA256, 90j)
- POST /api/mobile/auth/login: email+password → token + user
- GET /api/mobile/auth/me: valider token, retourner profil
- GET /api/mobile/notebooks: liste carnets avec nb notes
- GET /api/mobile/notes: notes récentes (filtre par carnet optionnel)
- GET /api/mobile/notes/[id]: contenu complet d'une note
- GET /api/mobile/search: recherche fulltext titre+contenu

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

memento-mobile/app/notebook/[id].tsx

@@ -0,0 +1,78 @@
+import { useEffect, useState } from 'react'
+import {
+  View, Text, FlatList, TouchableOpacity, ActivityIndicator, RefreshControl,
+} from 'react-native'
+import { SafeAreaView } from 'react-native-safe-area-context'
+import { useLocalSearchParams, useRouter } from 'expo-router'
+import { ArrowLeft } from 'lucide-react-native'
+import { apiFetch } from '@/lib/api'
+import { ENDPOINTS } from '@/lib/config'
+
+interface Note {
+  id: string
+  title: string
+  updatedAt: string
+}
+
+export default function NotebookScreen() {
+  const { id } = useLocalSearchParams<{ id: string }>()
+  const [notes, setNotes] = useState<Note[]>([])
+  const [notebookName, setNotebookName] = useState('')
+  const [loading, setLoading] = useState(true)
+  const [refreshing, setRefreshing] = useState(false)
+  const router = useRouter()
+
+  const load = async () => {
+    try {
+      const res = await apiFetch(ENDPOINTS.notes(id))
+      if (res.ok) {
+        const data = await res.json()
+        setNotes(data.notes ?? [])
+        setNotebookName(data.notebookName ?? '')
+      }
+    } finally {
+      setLoading(false)
+      setRefreshing(false)
+    }
+  }
+
+  useEffect(() => { load() }, [id])
+
+  return (
+    <SafeAreaView className="flex-1 bg-paper">
+      <View className="flex-row items-center gap-3 px-4 py-3 border-b border-border">
+        <TouchableOpacity onPress={() => router.back()} className="p-1">
+          <ArrowLeft size={22} color="#1A1A18" />
+        </TouchableOpacity>
+        <Text className="text-[17px] font-semibold text-ink flex-1">{notebookName || 'Carnet'}</Text>
+      </View>
+
+      {loading ? (
+        <View className="flex-1 items-center justify-center">
+          <ActivityIndicator color="#A47148" />
+        </View>
+      ) : (
+        <FlatList
+          data={notes}
+          keyExtractor={(item) => item.id}
+          contentContainerClassName="px-5 pt-4 pb-8"
+          refreshControl={<RefreshControl refreshing={refreshing} onRefresh={() => { setRefreshing(true); load() }} tintColor="#A47148" />}
+          renderItem={({ item }) => (
+            <TouchableOpacity
+              onPress={() => router.push(`/note/${item.id}`)}
+              className="bg-white border border-border rounded-2xl p-4 mb-2.5 active:opacity-70"
+            >
+              <Text className="text-[15px] font-semibold text-ink" numberOfLines={1}>
+                {item.title || 'Sans titre'}
+              </Text>
+              <Text className="text-[12px] text-concrete mt-0.5">
+                {new Date(item.updatedAt).toLocaleDateString('fr-FR', { day: 'numeric', month: 'short' })}
+              </Text>
+            </TouchableOpacity>
+          )}
+          ListEmptyComponent={<Text className="text-concrete text-center mt-12">Carnet vide.</Text>}
+        />
+      )}
+    </SafeAreaView>
+  )
+}