refactor(calendar): open native url schemes from meeting buttons

Open conference meetings directly via native app URL schemes instead of routing through the browser. Adds native scheme support for Zoom, Teams, FaceTime, and Discord with fallback to HTTPS.

DynamicIsland/components/Calendar/DynamicIslandCalendar.swift

@@ -1010,6 +1010,16 @@ enum ConferenceProvider: CaseIterable {
         }
     }
     
+    var nativeURLScheme: String? {
+        switch self {
+        case .zoom: return "zoommtg"
+        case .teams: return "msteams"
+        case .facetime: return "facetime"
+        case .discord: return "discord"
+        default: return nil
+        }
+    }
+
     static func detect(from url: URL) -> ConferenceProvider {
         let host = url.host?.lowercased() ?? ""
         return allCases.first { provider in
@@ -1035,7 +1045,17 @@ struct ConferenceJoinButton: View {
     }
     
     var body: some View {
-        Button(action: { openURL(url) }) {
+        Button(action: {
+            if let scheme = provider.nativeURLScheme,
+               var components = URLComponents(url: url, resolvingAgainstBaseURL: false) {
+                components.scheme = scheme
+                if let nativeURL = components.url {
+                    openURL(nativeURL)
+                    return
+                }
+            }
+            openURL(url)
+        }) {
             HStack(spacing: 4) {
                 Image(systemName: "video.fill")
                     .font(.system(size: 9))