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

backend/src/db/schema.ts

@@ -175,6 +175,33 @@ export const dailySummaries = pgTable("daily_summaries", {
 export type DailySummary = typeof dailySummaries.$inferSelect;
 export type NewDailySummary = typeof dailySummaries.$inferInsert;
 
+// ─── Personal Todos ───
+
+export const todoPriorityEnum = pgEnum("todo_priority", [
+  "high",
+  "medium",
+  "low",
+  "none",
+]);
+
+export const todos = pgTable("todos", {
+  id: uuid("id").defaultRandom().primaryKey(),
+  userId: text("user_id").notNull(),
+  title: text("title").notNull(),
+  description: text("description"),
+  isCompleted: boolean("is_completed").notNull().default(false),
+  priority: todoPriorityEnum("priority").notNull().default("none"),
+  category: text("category"),
+  dueDate: timestamp("due_date", { withTimezone: true }),
+  completedAt: timestamp("completed_at", { withTimezone: true }),
+  sortOrder: integer("sort_order").notNull().default(0),
+  createdAt: timestamp("created_at", { withTimezone: true }).defaultNow().notNull(),
+  updatedAt: timestamp("updated_at", { withTimezone: true }).defaultNow().notNull(),
+});
+
+export type Todo = typeof todos.$inferSelect;
+export type NewTodo = typeof todos.$inferInsert;
+
 // ─── BetterAuth tables ───
 
 export const users = pgTable("users", {