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/CornerComplicationViews.swift

@@ -0,0 +1,49 @@
+import SwiftUI
+import WidgetKit
+import CalendarrCore
+
+// A corner holds **one** value plus the curved bezel label. A second inner line
+// runs into the curved text — do not add one. `.widgetLabel` is what makes
+// WidgetKit lay the text along the edge; there is no arc to draw by hand.
+
+/// Value: live countdown. Label: time and title.
+struct CornerCountdownComplicationView: View {
+    let entry: WatchComplicationEntry
+
+    var body: some View {
+        let next = WatchComplicationSupport.nextEvent(in: entry.snapshot, at: entry.date)
+        Group {
+            if let next {
+                Text(WatchComplicationSupport.countdownTarget(next, at: entry.date), style: .timer)
+                    .widgetAccentable()
+            } else {
+                Image(systemName: "calendar")
+            }
+        }
+        .widgetLabel {
+            Text(WatchComplicationSupport.cornerLabel(next, at: entry.date, language: entry.language))
+        }
+    }
+}
+
+/// Value: the appointment's clock time. Label: the title.
+struct CornerTimeComplicationView: View {
+    let entry: WatchComplicationEntry
+
+    var body: some View {
+        let next = WatchComplicationSupport.nextEvent(in: entry.snapshot, at: entry.date)
+        Group {
+            if let next {
+                Text(next.isAllDay
+                     ? WatchL10n.t("watch.allday", entry.language)
+                     : WatchComplicationSupport.time(next.start, language: entry.language))
+                    .widgetAccentable()
+            } else {
+                Image(systemName: "calendar")
+            }
+        }
+        .widgetLabel {
+            Text(next?.title ?? WatchL10n.t("watch.no_events", entry.language))
+        }
+    }
+}