Widget system Phase 2: full cutover to widget-based rendering

device.py's mode-keyed dispatch is replaced by a real compositor:
load a frame's widgets, compute pixel rects via app/grid.py, render
each through its widget module, and composite with render_panel.
Physical NEXT/BACK buttons now execute each frame's assigned
FrameButtonAction rows instead of one hardcoded per-mode action.

api_frames.py, manage.py, and common.py's build_manage_content are
repointed to read/write the frame's widget config rows instead of
the old Frame columns, and every settings page (Photos/Calendar/
Whiteboard tabs) now pre-fills its form from the same widget config
the write endpoints actually save to -- previously the read and
write sides would have silently diverged. The old mode selector and
photo-inlay checkbox are removed along with their now-inert wiring;
arbitrary widget placement subsumes what the fixed inlay split did.

Ships together with Phase 1 (per-type render/action modules) since
splitting the read/write cutover across deploys would have left
settings changes with no visible effect.

server/tests/test_widgets_calendar.py

@@ -100,3 +100,28 @@ def test_back_action_decrements_browse_offset(db_session):
     widgets.calendar.ACTIONS["back"](db_session, frame, widget)
     cfg = db_session.get(CalendarWidgetConfig, widget.id)
     assert cfg.browse_offset == 2
+
+
+def test_normal_wake_resets_browse_offset_to_zero(db_session, monkeypatch):
+    """A plain /frame/image GET (is_normal_wake=True, the default) should
+    snap browse_offset back to "today" if a previous button press had
+    moved it -- mirrors the old _render_calendar_mode's identical
+    behavior. A button-triggered render (is_normal_wake=False) must NOT
+    do this, or every button press would immediately erase its own
+    effect on the very next render."""
+    frame, widget = _make_widget(db_session, view="week", browse_offset=5)
+    _stub_fetches(monkeypatch)
+
+    widgets.calendar.render(db_session, frame, widget, 400, 300, is_normal_wake=True)
+    assert db_session.get(CalendarWidgetConfig, widget.id).browse_offset == 0
+
+
+def test_button_triggered_render_does_not_reset_browse_offset(db_session, monkeypatch):
+    frame, widget = _make_widget(db_session, view="week", browse_offset=0)
+    _stub_fetches(monkeypatch)
+
+    widgets.calendar.ACTIONS["advance"](db_session, frame, widget)
+    assert db_session.get(CalendarWidgetConfig, widget.id).browse_offset == 1
+
+    widgets.calendar.render(db_session, frame, widget, 400, 300, is_normal_wake=False)
+    assert db_session.get(CalendarWidgetConfig, widget.id).browse_offset == 1