refactor: harden calendar sync and add dashboard widget

src/govoplan_calendar/backend/manifest.py

@@ -25,6 +25,7 @@ from govoplan_core.core.modules import (
     PermissionDefinition,
     RoleTemplate,
 )
+from govoplan_core.core.views import ViewSurface
 from govoplan_core.db.base import Base
 
 
@@ -204,6 +205,15 @@ manifest = ModuleManifest(
             ),
         ),
         nav_items=(NavItem(path="/calendar", label="Calendar", icon="calendar", required_any=("calendar:event:read",), order=55),),
+        view_surfaces=(
+            ViewSurface(
+                id="calendar.widget.upcoming",
+                module_id="calendar",
+                kind="section",
+                label="Upcoming events widget",
+                order=40,
+            ),
+        ),
     ),
     migration_spec=MigrationSpec(
         module_id="calendar",