feat(weekend): show next China statutory holiday countdown

Adds HolidayDatabase with 7 entries for 2026 (元旦/春节/清明/五一/
端午/中秋·国庆 + 2027 元旦 roll-over). WorkerStore.nextHoliday
computed returns the upcoming or currently-ongoing holiday with
days-until. WeekendView gains a tomato-tinted card under the
weekend hero showing "下个法定假 国庆 · 放 8 天 · X 天后" — or
"假期中" + 🎉 when the user opens the panel during the window.

Dates are estimated from typical State Council patterns; the file
header carries a TODO to verify against the official announcement
each year.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Sources/engine/Holidays.swift

@@ -0,0 +1,86 @@
+//
+//  Holidays.swift
+//  摸鱼侠 plugin v0.3.0
+//
+//  China State Council statutory holidays 2026. Estimated from prior-
+//  year patterns (公历日期固定假 + 农历节假) — exact dates and
+//  adjusted-workday days may shift when the State Council announces
+//  each year's calendar (typically Q4 of the prior year).
+//
+//  Data structure is a flat list rather than a JSON resource so the
+//  plugin bundle stays single-binary and dependency-free. To update:
+//  edit this file when the next year's official 国务院办公厅
+//  announcement publishes.
+//
+
+import Foundation
+
+struct Holiday {
+    /// "元旦" / "春节" / "国庆" / etc.
+    let name: String
+    /// First day of the holiday window (yyyy-MM-dd, Asia/Shanghai).
+    let startDate: String
+    /// Total consecutive days off, including the trigger day. e.g.
+    /// 国庆 = 8 covers 10/01-10/08 (when paired with 中秋 in 2026).
+    let days: Int
+}
+
+/// Resolved upcoming holiday with the days remaining and start Date.
+struct UpcomingHoliday {
+    let name: String
+    let startDate: Date
+    let days: Int
+    /// Days from now to startDate. 0 = today is day 1 of the holiday.
+    let daysUntil: Int
+    /// True when "now" falls inside [startDate, startDate+days).
+    let isOngoing: Bool
+}
+
+enum HolidayDatabase {
+    /// 2026 法定假期 — estimated from typical State Council pattern.
+    /// **Verify against the official 国务院办公厅 announcement.**
+    static let entries2026: [Holiday] = [
+        Holiday(name: "元旦",   startDate: "2026-01-01", days: 1),
+        Holiday(name: "春节",   startDate: "2026-02-17", days: 7),
+        Holiday(name: "清明",   startDate: "2026-04-04", days: 3),
+        Holiday(name: "五一",   startDate: "2026-05-01", days: 5),
+        Holiday(name: "端午",   startDate: "2026-06-19", days: 3),
+        Holiday(name: "中秋·国庆", startDate: "2026-10-01", days: 8),
+        // Roll-over to early 2027 so late-Dec users still see a next
+        // holiday after the 2026 calendar runs out.
+        Holiday(name: "元旦",   startDate: "2027-01-01", days: 3),
+    ]
+
+    /// Returns the soonest upcoming or currently-ongoing holiday.
+    /// `now` is injectable for testability.
+    static func upcoming(from now: Date, timeZone: TimeZone) -> UpcomingHoliday? {
+        let fmt = DateFormatter()
+        fmt.locale = Locale(identifier: "en_US_POSIX")
+        fmt.timeZone = timeZone
+        fmt.dateFormat = "yyyy-MM-dd"
+        var cal = Calendar(identifier: .gregorian)
+        cal.timeZone = timeZone
+        for h in entries2026 {
+            guard let start = fmt.date(from: h.startDate) else { continue }
+            guard let end = cal.date(byAdding: .day, value: h.days, to: start) else { continue }
+            if now >= start && now < end {
+                // In the holiday window already.
+                return UpcomingHoliday(
+                    name: h.name, startDate: start,
+                    days: h.days, daysUntil: 0, isOngoing: true
+                )
+            }
+            if start > now {
+                // Floor-divide of seconds to days for an integer answer
+                // independent of locale calendar shenanigans.
+                let secs = start.timeIntervalSince(now)
+                let daysUntil = Int(ceil(secs / 86400.0))
+                return UpcomingHoliday(
+                    name: h.name, startDate: start,
+                    days: h.days, daysUntil: daysUntil, isOngoing: false
+                )
+            }
+        }
+        return nil
+    }
+}

Sources/engine/WorkerStore.swift

@@ -683,6 +683,13 @@ final class WorkerStore: ObservableObject {
     /// True iff today is Saturday or Sunday (local time). Used by
     /// ClockoutView to switch to a "今天不上班" mode without forcing
     /// the user to fiddle with their clockout time on the weekend.
+    /// Next statutory China holiday, or nil if none configured.
+    /// Backed by `HolidayDatabase`. WeekendView uses this to render
+    /// the "距下个法定假 N 天" card.
+    var nextHoliday: UpcomingHoliday? {
+        HolidayDatabase.upcoming(from: Date(), timeZone: calendar.timeZone)
+    }
+
     var isWeekend: Bool {
         let weekday = calendar.component(.weekday, from: Date())
         return weekday == 1 || weekday == 7  // Sun = 1, Sat = 7

Sources/ui/WeekendView.swift

@@ -11,13 +11,18 @@ struct WeekendView: View {
     @ObservedObject var store: WorkerStore
 
     var body: some View {
-        VStack(spacing: 18) {
+        ScrollView {
+            VStack(spacing: 14) {
                 statusBadge
 
                 heroCountdown
 
                 partsRow
 
+                if store.nextHoliday != nil {
+                    holidayCard
+                }
+
                 Divider()
                     .background(WorkerTheme.overlay08)
                     .padding(.horizontal, 24)
@@ -27,6 +32,80 @@ struct WeekendView: View {
                 Spacer(minLength: 0)
             }
             .padding(.top, 8)
+            .padding(.bottom, 12)
+        }
+    }
+
+    // MARK: - Holiday card (next 法定假)
+
+    /// Distance-to-next-statutory-holiday card. Splits visual weight
+    /// with the weekend hero so users on a Friday don't just see "1 天
+    /// 2 时" and miss that 国庆放 8 天 is next week.
+    private var holidayCard: some View {
+        Group {
+            if let h = store.nextHoliday {
+                holidayContent(h)
+            }
+        }
+        .padding(.horizontal, 16)
+    }
+
+    @ViewBuilder
+    private func holidayContent(_ h: UpcomingHoliday) -> some View {
+        HStack(alignment: .center, spacing: 12) {
+            // Left side: name + days-off line
+            VStack(alignment: .leading, spacing: 4) {
+                HStack(spacing: 6) {
+                    Image(systemName: "party.popper.fill")
+                        .font(.system(size: 11, weight: .semibold))
+                        .foregroundColor(WorkerTheme.tomato)
+                    Text(h.isOngoing ? "假期中" : "下个法定假")
+                        .font(.system(size: 10.5, weight: .medium))
+                        .foregroundColor(WorkerTheme.fg55)
+                        .tracking(0.3)
+                }
+                Text(h.name)
+                    .font(.system(size: 15, weight: .bold))
+                    .foregroundColor(WorkerTheme.fgPrimary)
+                Text("放 \(h.days) 天")
+                    .font(.system(size: 11))
+                    .foregroundColor(WorkerTheme.fg55)
+            }
+            Spacer(minLength: 0)
+            // Right side: distance / "假期中"
+            VStack(alignment: .trailing, spacing: 2) {
+                if h.isOngoing {
+                    Text("🎉")
+                        .font(.system(size: 28))
+                } else {
+                    Text("\(h.daysUntil)")
+                        .font(.system(size: 30, weight: .bold, design: .rounded))
+                        .foregroundColor(WorkerTheme.tomato)
+                        .monospacedDigit()
+                    Text("天后")
+                        .font(.system(size: 10))
+                        .foregroundColor(WorkerTheme.fg55)
+                }
+            }
+        }
+        .padding(.horizontal, 14)
+        .padding(.vertical, 12)
+        .background(
+            RoundedRectangle(cornerRadius: 12)
+                .fill(
+                    LinearGradient(
+                        colors: [
+                            WorkerTheme.tomato.opacity(0.10),
+                            WorkerTheme.tomato.opacity(0.02)
+                        ],
+                        startPoint: .topLeading, endPoint: .bottomTrailing
+                    )
+                )
+                .overlay(
+                    RoundedRectangle(cornerRadius: 12)
+                        .stroke(WorkerTheme.tomato.opacity(0.30), lineWidth: 0.5)
+                )
+        )
     }
 
     // MARK: - Status