feat: Add comprehensive todo management system with Gemini-powered brain dump analysis

- Add TodoEntity, TodoDao, TodoRepository, and TodoRepositoryImpl for local todo storage with sync support
- Implement TodoViewModel with CRUD operations, group management, and subtask handling
- Create TodoScreen with Kanban-style board view, group-based organization, and drag-to-reorder support
- Add BrainDumpSheet for AI-powered task extraction from natural language input using Gemini API
- Implement TodoNot

app/src/main/java/com/shaarit/presentation/nav/NavGraph.kt

@@ -48,6 +48,7 @@ sealed class Screen(val route: String) {
         fun createRoute(linkId: Int): String = "reader/$linkId"
     }
     object Reminders : Screen("reminders")
+    object Todo : Screen("todo")
 }
 
 @Composable
@@ -154,7 +155,6 @@ fun AppNavGraph(
                 onNavigateToTags = { navController.navigate(Screen.Tags.route) },
                 onNavigateToCollections = { navController.navigate(Screen.Collections.route) },
                 onNavigateToSettings = { navController.navigate(Screen.Settings.route) },
-                onNavigateToRandom = { },
                 onNavigateToHelp = { navController.navigate(Screen.Help.route) },
                 onNavigateToDeadLinks = { navController.navigate(Screen.DeadLinks.route) },
                 onNavigateToPinned = { navController.navigate(Screen.Pinned.route) },
@@ -162,6 +162,7 @@ fun AppNavGraph(
                     navController.navigate(Screen.Reader.createRoute(linkId))
                 },
                 onNavigateToReminders = { navController.navigate(Screen.Reminders.route) },
+                onNavigateToTodo = { navController.navigate(Screen.Todo.route) },
                 onPlayAudio = onPlayAudio,
                 initialTagFilter = tag,
                 initialCollectionId = collectionId
@@ -343,5 +344,16 @@ fun AppNavGraph(
                 }
             )
         }
+
+        composable(
+            route = Screen.Todo.route,
+            deepLinks = listOf(
+                navDeepLink { uriPattern = "shaarit://todo" }
+            )
+        ) {
+            com.shaarit.presentation.todo.TodoScreen(
+                onNavigateBack = { navController.popBackStack() }
+            )
+        }
     }
 }