feat(widget): calendar filter config + fix group-view data leak

Bug fix: publishWidgetSnapshot() now guards against activeGroup != nil,
so group view events/colors never contaminate the widget cache.

Feature: widgets can now be configured via long-press → Edit Widget.
- WidgetCalendar struct + writeCalendars/readCalendars in WidgetData.swift
- calendarKey added to WidgetEvent (backward-compatible decoder)
- CalendarIntent.swift: CalendarAppEntity + CalendarEntityQuery + CalendarSelectionIntent
- CalendarrTimelineProvider migrated from TimelineProvider to AppIntentTimelineProvider
- All 13 StaticConfiguration widgets changed to AppIntentConfiguration
- publishWidgetSnapshot() builds + writes the calendar list for the intent

An empty selection (default) shows all calendars; selecting specific
calendars filters the widget events accordingly.

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

Shared/WidgetData.swift

@@ -8,6 +8,14 @@ import WidgetKit
 /// and the App Group ID registered in the Apple Developer Portal.
 let widgetAppGroupID = "group.com.scarriffleservices.calendarr"
 
+/// Lightweight calendar descriptor stored alongside the event cache so the
+/// widget configuration intent can offer calendar options without a network call.
+struct WidgetCalendar: Codable, Identifiable, Hashable {
+    let id: String       // calendarKey ("source-calendarId")
+    let name: String
+    let colorHex: String
+}
+
 /// Lightweight event representation that lives inside the widget cache.
 /// We strip everything the widget doesn't need (notes, calendar IDs, URLs).
 struct WidgetEvent: Codable, Hashable, Identifiable {
@@ -18,6 +26,27 @@ struct WidgetEvent: Codable, Hashable, Identifiable {
     let isAllDay: Bool
     let colorHex: String
     let location: String
+    let calendarKey: String   // used for per-calendar filtering in widget config
+
+    init(id: String, title: String, start: Date, end: Date,
+         isAllDay: Bool, colorHex: String, location: String, calendarKey: String) {
+        self.id = id; self.title = title; self.start = start; self.end = end
+        self.isAllDay = isAllDay; self.colorHex = colorHex
+        self.location = location; self.calendarKey = calendarKey
+    }
+
+    // Backward-compatible decoder: old caches have no calendarKey field.
+    init(from decoder: Decoder) throws {
+        let c = try decoder.container(keyedBy: CodingKeys.self)
+        id         = try c.decode(String.self, forKey: .id)
+        title      = try c.decode(String.self, forKey: .title)
+        start      = try c.decode(Date.self,   forKey: .start)
+        end        = try c.decode(Date.self,   forKey: .end)
+        isAllDay   = try c.decode(Bool.self,   forKey: .isAllDay)
+        colorHex   = try c.decode(String.self, forKey: .colorHex)
+        location   = try c.decode(String.self, forKey: .location)
+        calendarKey = try c.decodeIfPresent(String.self, forKey: .calendarKey) ?? ""
+    }
 }
 
 /// Snapshot blob the app writes to the App-Group container and the widget reads.
@@ -75,7 +104,8 @@ struct WidgetSnapshot: Codable {
 }
 
 enum WidgetStore {
-    private static let cacheFilename = "widget-cache.json"
+    private static let cacheFilename     = "widget-cache.json"
+    private static let calendarsFilename = "widget-calendars.json"
 
     private static var containerURL: URL? {
         FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: widgetAppGroupID)
@@ -85,6 +115,10 @@ enum WidgetStore {
         containerURL?.appendingPathComponent(cacheFilename)
     }
 
+    private static var calendarsURL: URL? {
+        containerURL?.appendingPathComponent(calendarsFilename)
+    }
+
     /// Called by the app whenever the event cache changes.
     static func write(_ snapshot: WidgetSnapshot) {
         guard let url = cacheURL else { return }
@@ -103,6 +137,21 @@ enum WidgetStore {
         return try? decoder.decode(WidgetSnapshot.self, from: data)
     }
 
+    /// Write the list of available calendars so the widget intent can offer
+    /// calendar options for filtering without a network call.
+    static func writeCalendars(_ calendars: [WidgetCalendar]) {
+        guard let url = calendarsURL else { return }
+        if let data = try? JSONEncoder().encode(calendars) {
+            try? data.write(to: url, options: .atomic)
+        }
+    }
+
+    /// Read the calendar list written by the main app.
+    static func readCalendars() -> [WidgetCalendar] {
+        guard let url = calendarsURL, let data = try? Data(contentsOf: url) else { return [] }
+        return (try? JSONDecoder().decode([WidgetCalendar].self, from: data)) ?? []
+    }
+
     /// Rewrite the existing snapshot with the latest colour / language values
     /// from UserDefaults. Used when the user tweaks an appearance setting and
     /// we want the widgets to refresh immediately, without needing a new event