feat: UI redesign with park detail pages and ride status

Visual overhaul:
- Warmer color system with amber accent for Today, better text hierarchy
- Row hover highlighting, sticky column shadow on horizontal scroll
- Closed cells replaced with dot (·) instead of "Closed" text
- Regional grouping (Northeast/Southeast/Midwest/Texas & South/West)
- Two-row header with park count badge and WeekNav on separate lines
- Amber "Today" button in WeekNav when off current week
- Mobile card layout (< 1024px) with 7-day grid per park; table on desktop
- Skeleton loading state via app/loading.tsx

Park detail pages (/park/[id]):
- Month calendar view with ← → navigation via ?month= param
- Live ride status fetched from Six Flags API (cached 1h)
- Ride hours only shown when they differ from park operating hours
- Fallback to nearest upcoming open day when today is dropped by API,
  including cross-month fallback for end-of-month edge case

Data layer:
- Park type gains region field; parks.ts exports groupByRegion()
- db.ts gains getParkMonthData() for single-park month queries
- sixflags.ts gains scrapeRidesForDay() returning RidesFetchResult
  with rides, dataDate, isExact, and parkHoursLabel

Removed: CalendarGrid.tsx, MonthNav.tsx (dead code)

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

components/Legend.tsx

@@ -0,0 +1,33 @@
+export function Legend() {
+  return (
+    <div style={{
+      display: "flex",
+      alignItems: "center",
+      gap: 16,
+      fontSize: "0.72rem",
+      color: "var(--color-text-muted)",
+      flexShrink: 0,
+    }}>
+      <span style={{ display: "flex", alignItems: "center", gap: 5 }}>
+        <span style={{
+          display: "inline-block", width: 28, height: 14, borderRadius: 3,
+          background: "var(--color-open-bg)", border: "1px solid var(--color-open-border)",
+        }} />
+        Open
+      </span>
+      <span style={{ display: "flex", alignItems: "center", gap: 5 }}>
+        <span style={{
+          display: "inline-block", width: 28, height: 14, borderRadius: 3,
+          background: "var(--color-ph-bg)", border: "1px solid var(--color-ph-border)",
+        }} />
+        Passholder
+      </span>
+      <span style={{ display: "flex", alignItems: "center", gap: 6 }}>
+        <span style={{ color: "var(--color-text-dim)" }}>·</span>
+        <span style={{ color: "var(--color-text-dim)" }}>Closed</span>
+        <span style={{ color: "var(--color-border)" }}>·</span>
+        <span style={{ color: "var(--color-text-dim)" }}>— no data</span>
+      </span>
+    </div>
+  );
+}