maven: fix test mocks for CalendarEvents interface (verification)

- Add CalendarEvents method to recordingAPI in auth_test.go
- Add CalendarEvents method to fakeCore in handlers_test.go

Co-Authored-By: opencode <opencode@anthropic.com>

cmd/mavweb/handlers_test.go

@@ -116,6 +116,9 @@ func (f *fakeCore) RecentFacts(_ context.Context, _ int) ([]ipc.Fact, error) {
 	}
 	return f.facts, nil
 }
+func (f *fakeCore) CalendarEvents(_ context.Context, _, _ time.Time) ([]ipc.Fact, error) {
+	return nil, nil
+}
 
 func (f *fakeCore) RecentNudges(_ context.Context, _ int) ([]ipc.Nudge, error) {
 	if f.nudgesErr != nil {