Add the watch app and its eight complications

The watch receives the phone's payload over WatchConnectivity and writes it
into its own App Group container through the same SnapshotStore, so there is
one wire format and one reader. The agenda, the detail screen and the filter
all read that; the complications read what the app last wrote, since an
extension cannot run a WCSession of its own.

Complication timelines land on event boundaries rather than a schedule, so the
next appointment flips in the exact minute it changes without spending refresh
budget.

CalendarrWatchShared holds what both watch targets need, attached to each the
way Shared/ is attached to the app and the widgets.

recommendations() is implemented because watchOS requires it — iOS has a
default, the watch does not, since the complication gallery has to be
populated. Found by building, not by reading.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CalendarrWatchComplications/WatchComplicationSupport.swift

@@ -0,0 +1,58 @@
+import Foundation
+import CalendarrCore
+
+enum WatchComplicationSupport {
+    /// The first event that has not ended yet — including one running now,
+    /// which is what "what is next" means when you are already in a meeting.
+    /// Matches `WatchPushPolicy.nextEventIdentity`, deliberately.
+    static func nextEvent(in snapshot: CalendarrSnapshot?, at now: Date) -> SnapshotEvent? {
+        snapshot?.events.filter { $0.end > now }.min { $0.start < $1.start }
+    }
+
+    static func upcoming(in snapshot: CalendarrSnapshot?, at now: Date, limit: Int) -> [SnapshotEvent] {
+        guard let snapshot else { return [] }
+        return Array(snapshot.events.filter { $0.end > now }.sorted { $0.start < $1.start }.prefix(limit))
+    }
+
+    static func todayCount(in snapshot: CalendarrSnapshot?, at now: Date,
+                           calendar: Calendar = Calendar(identifier: .gregorian)) -> Int {
+        guard let snapshot else { return 0 }
+        let dayStart = calendar.startOfDay(for: now)
+        guard let dayEnd = calendar.date(byAdding: .day, value: 1, to: dayStart) else { return 0 }
+        return snapshot.events.filter { $0.start < dayEnd && $0.end > dayStart }.count
+    }
+
+    /// What a countdown counts to: the start if it has not begun, otherwise the
+    /// end. Counting up from a start time that has passed reads as broken.
+    static func countdownTarget(_ event: SnapshotEvent, at now: Date) -> Date {
+        event.start > now ? event.start : event.end
+    }
+
+    /// How full a draining ring should be, over a two-hour lead window.
+    static func gaugeFraction(to target: Date, at now: Date) -> Double {
+        let window: TimeInterval = 2 * 3600
+        return min(1, max(0, target.timeIntervalSince(now) / window))
+    }
+
+    static func time(_ date: Date, language: String) -> String {
+        let formatter = DateFormatter()
+        formatter.locale = WatchL10n.locale(language)
+        formatter.dateFormat = "HH:mm"
+        return formatter.string(from: date)
+    }
+
+    static func monthAbbreviation(_ date: Date, language: String) -> String {
+        let formatter = DateFormatter()
+        formatter.locale = WatchL10n.locale(language)
+        formatter.dateFormat = "LLL"
+        return formatter.string(from: date).uppercased()
+    }
+
+    /// The curved bezel label for a corner complication: time plus title, or a
+    /// plain "no events".
+    static func cornerLabel(_ event: SnapshotEvent?, at now: Date, language: String) -> String {
+        guard let event else { return WatchL10n.t("watch.no_events", language) }
+        if event.isAllDay { return event.title }
+        return "\(time(event.start, language: language)) \(event.title)"
+    }
+}