feat: add personal todos feature

- New todos table in DB schema (title, description, priority, category, due date, completion)
- Full CRUD + toggle API routes at /api/todos
- Categories support with filtering
- Bulk import endpoint for migration
- New TodosPage with inline editing, priority badges, due date display
- Add Todos to sidebar navigation
- Dark mode support throughout

frontend/src/lib/api.ts

@@ -1,4 +1,4 @@
-import type { Task, Project, ProjectWithTasks, VelocityStats, Recurrence } from "./types";
+import type { Task, Project, ProjectWithTasks, VelocityStats, Recurrence, Todo, TodoPriority } from "./types";
 
 const BASE = "/api/tasks";
 
@@ -228,3 +228,75 @@ export async function deleteUser(userId: string): Promise<void> {
   });
   if (!res.ok) throw new Error("Failed to delete user");
 }
+
+// ─── Todos API ───
+
+const TODOS_BASE = "/api/todos";
+
+export async function fetchTodos(params?: { completed?: string; category?: string }): Promise<Todo[]> {
+  const url = new URL(TODOS_BASE, window.location.origin);
+  if (params?.completed) url.searchParams.set("completed", params.completed);
+  if (params?.category) url.searchParams.set("category", params.category);
+  const res = await fetch(url.toString(), { credentials: "include" });
+  if (!res.ok) throw new Error(res.status === 401 ? "Unauthorized" : "Failed to fetch todos");
+  return res.json();
+}
+
+export async function fetchTodoCategories(): Promise<string[]> {
+  const res = await fetch(`${TODOS_BASE}/categories`, { credentials: "include" });
+  if (!res.ok) throw new Error("Failed to fetch categories");
+  return res.json();
+}
+
+export async function createTodo(todo: {
+  title: string;
+  description?: string;
+  priority?: TodoPriority;
+  category?: string;
+  dueDate?: string | null;
+}): Promise<Todo> {
+  const res = await fetch(TODOS_BASE, {
+    method: "POST",
+    credentials: "include",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(todo),
+  });
+  if (!res.ok) throw new Error("Failed to create todo");
+  return res.json();
+}
+
+export async function updateTodo(id: string, updates: Partial<{
+  title: string;
+  description: string;
+  priority: TodoPriority;
+  category: string | null;
+  dueDate: string | null;
+  isCompleted: boolean;
+  sortOrder: number;
+}>): Promise<Todo> {
+  const res = await fetch(`${TODOS_BASE}/${id}`, {
+    method: "PATCH",
+    credentials: "include",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(updates),
+  });
+  if (!res.ok) throw new Error("Failed to update todo");
+  return res.json();
+}
+
+export async function toggleTodo(id: string): Promise<Todo> {
+  const res = await fetch(`${TODOS_BASE}/${id}/toggle`, {
+    method: "PATCH",
+    credentials: "include",
+  });
+  if (!res.ok) throw new Error("Failed to toggle todo");
+  return res.json();
+}
+
+export async function deleteTodo(id: string): Promise<void> {
+  const res = await fetch(`${TODOS_BASE}/${id}`, {
+    method: "DELETE",
+    credentials: "include",
+  });
+  if (!res.ok) throw new Error("Failed to delete todo");
+}