Extract shared types to src/types/dashboard.ts

Consolidate duplicated type definitions (User, Settings, Widget,
CalendarEvent, CalendarSource, NoteBoardItem, etc.) into a single
shared types file. Removes ~100 lines of duplicated type code across
page.tsx, settings/page.tsx, NoteWidget.tsx, and CalendarWidget.tsx.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/CalendarWidget.tsx

@@ -1,22 +1,7 @@
 "use client";
 
 import { useMemo, useState } from "react";
-
-type CalendarEvent = {
-  id: string;
-  title: string;
-  start: string;
-  end: string | null;
-  location: string | null;
-};
-
-type CalendarSource = {
-  id: string;
-  name: string;
-  color: string;
-  type: string;
-  passwordConfigured: boolean;
-};
+import type { CalendarEvent, CalendarSource } from "@/types/dashboard";
 
 type CalendarWidgetProps = {
   widgetId: string;