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/ParkMonthCalendar.tsx

@@ -187,7 +187,10 @@ export function ParkMonthCalendar({ parkId, year, month, monthData, today, timez
                         Passholder
                       </div>
                       <div style={{ fontSize: "0.65rem", color: "var(--color-ph-hours)", marginTop: 2 }}>
-                        {dayData.hoursLabel} {tzAbbr}
+                        {dayData.hoursLabel}
+                      </div>
+                      <div style={{ fontSize: "0.58rem", color: "var(--color-ph-label)", opacity: 0.75, marginTop: 1, letterSpacing: "0.04em" }}>
+                        {tzAbbr}
                       </div>
                     </div>
                   ) : isOpen ? (
@@ -198,7 +201,10 @@ export function ParkMonthCalendar({ parkId, year, month, monthData, today, timez
                       padding: "3px 6px",
                     }}>
                       <div style={{ fontSize: "0.65rem", color: "var(--color-open-hours)" }}>
-                        {dayData.hoursLabel} {tzAbbr}
+                        {dayData.hoursLabel}
+                      </div>
+                      <div style={{ fontSize: "0.58rem", color: "var(--color-open-hours)", opacity: 0.6, marginTop: 1, letterSpacing: "0.04em" }}>
+                        {tzAbbr}
                       </div>
                     </div>
                   ) : (