views: move agenda view to main area

This prepares for multiple views to be there for mobile
users, and is the location at which a dedicated agenda
view for desktop will be, once the current agenda view
is refactored to suit desktop use-cases better.

Signed-off-by: Markus Göllnitz <camelcasenick@bewares.it>
Part-of: <https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/542>

src/gui/views/gcal-agenda-view.ui

@@ -2,6 +2,14 @@
 <interface>
   <template class="GcalAgendaView" parent="GtkBox">
     <property name="orientation">vertical</property>
+    <child>
+      <object class="GcalDateChooser" id="date_chooser">
+        <property name="split-month-year">False</property>
+        <property name="vexpand">False</property>
+        <property name="valign">end</property>
+        <property name="active-date" bind-source="GcalAgendaView" bind-property="active-date" bind-flags="bidirectional" />
+      </object>
+    </child>
     <child>
       <object class="GtkScrolledWindow" id="scrolled_window">
         <property name="hexpand">True</property>
@@ -12,9 +20,6 @@
             <property name="selection-mode">none</property>
             <property name="vexpand">True</property>
             <signal name="row-activated" handler="on_list_box_row_activated_cb" object="GcalAgendaView" swapped="no" />
-            <style>
-              <class name="background" />
-            </style>
             <child>
               <object class="GtkListBoxRow" id="no_events_row">
                 <property name="activatable">False</property>