refactor: make frontend a pure presentation layer fetching from backend API

Server components now fetch composed data from the backend instead of
directly querying SQLite and external APIs. Removes better-sqlite3
dependency from the frontend entirely.

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

components/ParkMonthCalendar.tsx

@@ -1,5 +1,5 @@
 import Link from "next/link";
-import type { DayData } from "@/lib/db";
+import type { DayData } from "@/lib/types";
 import { getTimezoneAbbr } from "@/lib/env";
 
 interface ParkMonthCalendarProps {