feat: add Hono backend API server with tiered scheduler

Standalone Node.js backend that owns the SQLite database and serves
composed data via REST endpoints. Replaces the shell-scheduled scraper
with in-process node-cron tiered scheduling.

Backend structure:
- Hono HTTP server on port 3001 with CORS and request logging
- Singleton SQLite connection with WAL mode
- In-memory TTL cache for Queue-Times and fetchToday responses
- Comparison check on fetchToday (read-before-write, only upserts on change)

API endpoints:
- GET /api/calendar/week — week schedule + live ride counts for all parks
- GET /api/calendar/:parkId/month — month calendar for one park
- GET /api/parks — park list with metadata
- GET /api/parks/:id — single park detail
- GET /api/parks/:id/rides — live rides with Queue-Times/schedule fallback
- GET /api/status — health check, scrape stats
- POST /api/scrape/trigger — manual scrape (scope: today/month/upcoming/full)

Scheduler tiers:
- Tier 1: today — hourly (Mar-Dec)
- Tier 2: current month — every 6 hours
- Tier 3: upcoming — twice daily (3 AM + 3 PM)
- Tier 4: full year — daily at 3 AM

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

backend/src/services/cache.ts

@@ -0,0 +1,35 @@
+interface CacheEntry<T> {
+  data: T;
+  expiresAt: number;
+}
+
+export class TtlCache<T> {
+  private store = new Map<string, CacheEntry<T>>();
+
+  constructor(private defaultTtlMs: number) {}
+
+  get(key: string): T | null {
+    const entry = this.store.get(key);
+    if (!entry) return null;
+    if (Date.now() > entry.expiresAt) {
+      this.store.delete(key);
+      return null;
+    }
+    return entry.data;
+  }
+
+  set(key: string, data: T, ttlMs?: number): void {
+    this.store.set(key, {
+      data,
+      expiresAt: Date.now() + (ttlMs ?? this.defaultTtlMs),
+    });
+  }
+
+  clear(): void {
+    this.store.clear();
+  }
+
+  get size(): number {
+    return this.store.size;
+  }
+}