fix: resolve note todos synchronization issue between mobile and desktop

Fixed critical bug where todos added on mobile or desktop were being silently lost.

Root cause:
- Mobile and desktop were sending todos via the generic PUT /api/notes/:id endpoint
- Backend ignored the 'todos' field in this endpoint (only processes title and content)
- Users saw success messages but todos were never saved to database
- On reload, todos disappeared

Solution:
- Added dedicated todo management methods to NotesService:
  * addTodo() - POST /api/notes/:id/todos
  * updateTodo() - PUT /api/notes/todos/:todoId
  * toggleTodo() - PUT /api/notes/todos/:todoId
  * deleteTodo() - DELETE /api/notes/todos/:todoId

- Updated NoteDetailPage.tsx (mobile) to use proper API methods
- Updated Index.tsx (desktop) to use proper API methods
- Both versions now correctly persist todos to the database

Files modified:
- src/services/NotesService.ts - Added todo management methods
- src/pages/mobile/NoteDetailPage.tsx - Fixed todo handlers
- src/pages/Index.tsx - Fixed todo handlers in note detail view

src/pages/Index.tsx

@@ -1414,9 +1414,14 @@ const Index = () => {
                               <Checkbox
                                 checked={todo.completed}
                                 onCheckedChange={async () => {
+                                  if (!todo.id) return;
+                                  const success = await NotesService.toggleTodo(todo.id, !todo.completed);
+                                  if (success) {
                                     const updatedTodos = [...(openNote.todos || [])];
                                     updatedTodos[index] = { ...todo, completed: !todo.completed };
-                                  await handleUpdateNote({ todos: updatedTodos });
+                                    setOpenNote({ ...openNote, todos: updatedTodos });
+                                    setNotes(prev => prev.map(note => note.id === openNote.id ? { ...note, todos: updatedTodos } : note));
+                                  }
                                 }}
                               />
                               <span className={todo.completed ? "line-through text-muted-foreground flex-1 text-sm" : "flex-1 text-sm"}>
@@ -1427,9 +1432,14 @@ const Index = () => {
                                 size="icon"
                                 className="h-6 w-6"
                                 onClick={async () => {
-                                  const updatedTodos = [...(openNote.todos || [])];
-                                  updatedTodos.splice(index, 1);
-                                  await handleUpdateNote({ todos: updatedTodos });
+                                  if (!todo.id) return;
+                                  const success = await NotesService.deleteTodo(todo.id);
+                                  if (success) {
+                                    const updatedTodos = openNote.todos.filter((_, i) => i !== index);
+                                    setOpenNote({ ...openNote, todos: updatedTodos });
+                                    setNotes(prev => prev.map(note => note.id === openNote.id ? { ...note, todos: updatedTodos } : note));
+                                    showSuccess("Tâche supprimée");
+                                  }
                                 }}
                               >
                                 <Trash2 className="h-3 w-3" />
@@ -2215,9 +2225,13 @@ const Index = () => {
         label="Tâche"
         placeholder="Entrez la tâche..."
         onConfirm={async (text) => {
-          if (openNote) {
-            const updatedTodos = [...(openNote.todos || []), { text, completed: false }];
-            await handleUpdateNote({ todos: updatedTodos });
+          if (openNote?.id) {
+            const newTodo = await NotesService.addTodo(openNote.id, text);
+            if (newTodo) {
+              const updatedTodos = [...(openNote.todos || []), newTodo];
+              setOpenNote({ ...openNote, todos: updatedTodos });
+              setNotes(prev => prev.map(note => note.id === openNote.id ? { ...note, todos: updatedTodos } : note));
+            }
           }
         }}
         confirmText="Ajouter"

src/pages/mobile/NoteDetailPage.tsx

@@ -80,28 +80,40 @@ export default function NoteDetailPage() {
   };
 
   const handleAddTodo = async () => {
-    if (!note || !todoText.trim()) return;
-    const newTodo = { text: todoText, completed: false };
+    if (!note?.id || !todoText.trim()) return;
+    const newTodo = await NotesService.addTodo(note.id, todoText.trim());
+    if (newTodo) {
       const updatedTodos = [...(note.todos || []), newTodo];
-    await updateNote({ todos: updatedTodos });
+      setNote({ ...note, todos: updatedTodos });
       setTodoText("");
       setAddTodoModal(false);
-    showSuccess("Tâche ajoutée");
+    }
   };
 
   const handleToggleTodo = async (index: number) => {
     if (!note?.todos) return;
+    const todo = note.todos[index];
+    if (!todo.id) return;
+
+    const success = await NotesService.toggleTodo(todo.id, !todo.completed);
+    if (success) {
       const updatedTodos = [...note.todos];
       updatedTodos[index] = { ...updatedTodos[index], completed: !updatedTodos[index].completed };
-    await updateNote({ todos: updatedTodos });
+      setNote({ ...note, todos: updatedTodos });
+    }
   };
 
   const handleDeleteTodo = async (index: number) => {
     if (!note?.todos) return;
-    const updatedTodos = [...note.todos];
-    updatedTodos.splice(index, 1);
-    await updateNote({ todos: updatedTodos });
+    const todo = note.todos[index];
+    if (!todo.id) return;
+
+    const success = await NotesService.deleteTodo(todo.id);
+    if (success) {
+      const updatedTodos = note.todos.filter((_, i) => i !== index);
+      setNote({ ...note, todos: updatedTodos });
       showSuccess("Tâche supprimée");
+    }
   };
 
   const handleImageUpload = async (e: React.ChangeEvent<HTMLInputElement>) => {

src/services/NotesService.ts

@@ -219,6 +219,85 @@ class NotesService {
       return false;
     }
   }
+
+  // Todo management methods
+  async addTodo(noteId: number, text: string): Promise<Todo | null> {
+    try {
+      const response = await fetch(`/api/notes/${noteId}/todos`, {
+        method: "POST",
+        headers: AuthService.getHeaders(),
+        body: JSON.stringify({ text })
+      });
+
+      if (!response.ok) {
+        throw new Error("Erreur lors de l'ajout de la tâche");
+      }
+
+      const result = await response.json();
+      showSuccess("Tâche ajoutée");
+      return result.todo || result;
+    } catch (error) {
+      showError(error instanceof Error ? error.message : "Erreur serveur");
+      return null;
+    }
+  }
+
+  async updateTodo(todoId: number, updates: Partial<Todo>): Promise<Todo | null> {
+    try {
+      const response = await fetch(`/api/notes/todos/${todoId}`, {
+        method: "PUT",
+        headers: AuthService.getHeaders(),
+        body: JSON.stringify(updates)
+      });
+
+      if (!response.ok) {
+        throw new Error("Erreur lors de la mise à jour de la tâche");
+      }
+
+      const result = await response.json();
+      return result.todo || result;
+    } catch (error) {
+      showError(error instanceof Error ? error.message : "Erreur serveur");
+      return null;
+    }
+  }
+
+  async toggleTodo(todoId: number, completed: boolean): Promise<boolean> {
+    try {
+      const response = await fetch(`/api/notes/todos/${todoId}`, {
+        method: "PUT",
+        headers: AuthService.getHeaders(),
+        body: JSON.stringify({ completed })
+      });
+
+      if (!response.ok) {
+        throw new Error("Erreur lors de la mise à jour de la tâche");
+      }
+
+      return true;
+    } catch (error) {
+      showError(error instanceof Error ? error.message : "Erreur serveur");
+      return false;
+    }
+  }
+
+  async deleteTodo(todoId: number): Promise<boolean> {
+    try {
+      const response = await fetch(`/api/notes/todos/${todoId}`, {
+        method: "DELETE",
+        headers: AuthService.getHeaders()
+      });
+
+      if (!response.ok) {
+        throw new Error("Erreur lors de la suppression de la tâche");
+      }
+
+      return true;
+    } catch (error) {
+      showError(error instanceof Error ? error.message : "Erreur serveur");
+      return false;
+    }
+  }
 }
 
 export default new NotesService();