polish: clarify parks open badge; improve timezone display

- "parks open" → "parks open this week" for clarity
- Week calendar cells: stack hours above tz abbreviation (smaller,
  dimmer) instead of inline to avoid overflow in tight 130px columns
- Mobile park cards: tz abbreviation inline but smaller/dimmer (60% opacity)
- Month calendar: same two-line stacking in compact day cells

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

components/ParkCard.tsx

@@ -154,7 +154,10 @@ export function ParkCard({ park, weekDates, parkData, today, openRideCount, coas
                         ? "var(--color-today-text)"
                         : "var(--color-open-hours)",
                     }}>
-                      {dayData.hoursLabel} {tzAbbr}
+                      {dayData.hoursLabel}{" "}
+                      <span style={{ fontSize: "0.68rem", fontWeight: 400, opacity: 0.6 }}>
+                        {tzAbbr}
+                      </span>
                     </span>
                   </div>
                 </div>