feat: detect passholder preview days and filter plain buyouts

- Buyout days are now treated as closed unless they carry a Passholder
  Preview event, in which case they surface as a distinct purple cell
  in the UI showing "Passholder" + hours
- DB gains a special_type column (auto-migrated on next startup)
- scrape.ts threads specialType through to upsertDay
- debug.ts now shows events, isBuyout, isPassholderPreview, and
  specialType in the parsed result section

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

components/WeekCalendar.tsx

@@ -177,6 +177,52 @@ export function WeekCalendar({ parks, weekDates, data }: WeekCalendarProps) {
                     );
                   }
 
+                  // Passholder preview day
+                  if (dayData.specialType === "passholder_preview") {
+                    return (
+                      <td key={date} style={{
+                        ...tdBase,
+                        padding: 4,
+                        borderLeft: isToday ? "1px solid var(--color-today-border)" : undefined,
+                        borderRight: isToday ? "1px solid var(--color-today-border)" : undefined,
+                      }}>
+                        <div style={{
+                          background: "var(--color-ph-bg)",
+                          border: "1px solid var(--color-ph-border)",
+                          borderRadius: 6,
+                          padding: "4px 4px",
+                          textAlign: "center",
+                          height: "100%",
+                          display: "flex",
+                          flexDirection: "column",
+                          alignItems: "center",
+                          justifyContent: "center",
+                          gap: 2,
+                        }}>
+                          <span style={{
+                            color: "var(--color-ph-label)",
+                            fontSize: "0.6rem",
+                            fontWeight: 600,
+                            letterSpacing: "0.04em",
+                            textTransform: "uppercase",
+                            whiteSpace: "nowrap",
+                          }}>
+                            Passholder
+                          </span>
+                          <span style={{
+                            color: "var(--color-ph-hours)",
+                            fontSize: "0.72rem",
+                            fontWeight: 500,
+                            letterSpacing: "-0.01em",
+                            whiteSpace: "nowrap",
+                          }}>
+                            {dayData.hoursLabel}
+                          </span>
+                        </div>
+                      </td>
+                    );
+                  }
+
                   // Open with confirmed hours
                   return (
                     <td key={date} style={{