polish: mobile view layout and usability improvements

Header:
- Hide "X of Y parks open this week" badge on mobile (hidden sm:inline-flex)
  — title + Coaster Mode button fit cleanly on a 390px screen

WeekNav:
- Arrow button padding 6px 14px → 10px 16px, minWidth: 44px for proper
  touch targets (Apple HIG recommends 44px minimum)
- Date label minWidth 200px → 140px, prevents crowding on small screens

ParkCard:
- Name container: flex: 1, minWidth: 0 so long park names don't push
  the status badge off-screen; name wraps naturally instead of overflowing
- Timezone abbreviation: opacity: 0.6 → color: var(--color-text-dim),
  semantic dimming instead of opacity for better accessibility
- Passholder label: 0.58rem → 0.65rem (was below WCAG minimum)

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

components/WeekNav.tsx

@@ -75,7 +75,7 @@ export function WeekNav({ weekStart, weekDates, isCurrentWeek }: WeekNavProps) {
         fontSize: "1rem",
         fontWeight: 600,
         color: "var(--color-text)",
-        minWidth: 200,
+        minWidth: 140,
         textAlign: "center",
         letterSpacing: "-0.01em",
         fontVariantNumeric: "tabular-nums",
@@ -97,8 +97,8 @@ export function WeekNav({ weekStart, weekDates, isCurrentWeek }: WeekNavProps) {
 }
 
 const navBtnStyle: React.CSSProperties = {
-  padding: "6px 14px",
-  borderRadius: 6,
+  padding: "10px 16px",
+  borderRadius: 8,
   border: "1px solid var(--color-border)",
   background: "var(--color-surface)",
   color: "var(--color-text-muted)",
@@ -106,11 +106,13 @@ const navBtnStyle: React.CSSProperties = {
   fontSize: "1rem",
   lineHeight: 1,
   transition: "background 150ms ease, border-color 150ms ease, color 150ms ease",
+  minWidth: 44,
+  textAlign: "center",
 };
 
 const navBtnHover: React.CSSProperties = {
-  padding: "6px 14px",
-  borderRadius: 6,
+  padding: "10px 16px",
+  borderRadius: 8,
   border: "1px solid var(--color-text-dim)",
   background: "var(--color-surface-2)",
   color: "var(--color-text-secondary)",
@@ -118,6 +120,8 @@ const navBtnHover: React.CSSProperties = {
   fontSize: "1rem",
   lineHeight: 1,
   transition: "background 150ms ease, border-color 150ms ease, color 150ms ease",
+  minWidth: 44,
+  textAlign: "center",
 };
 
 const todayBtnStyle: React.CSSProperties = {