First step of replacing Frame.mode (one renderer owns the whole panel) with an Android-home-screen-style widget system -- a frame will hold N independently placed/sized widgets (photos/calendar/whiteboard), each with its own config/state, plus fully user-assignable NEXT/BACK button actions. Full plan at .claude/plans/prancy-snacking-iverson.md. This phase is additive only and changes no existing behavior -- nothing reads these new tables yet: - models.py: Widget (placement) + PhotoWidgetConfig/CalendarWidgetConfig/ WhiteboardWidgetConfig (per-type 1:1 extension tables, matching this codebase's existing convention of dedicated tables for naturally-scoped state rather than one wide table) + FrameButtonAction (ordered (widget, action) bindings per physical button). - grid.py: pure snap-to-grid placement math, defined relative to the panel's long/short axis so it stays valid across logical_render_size(orientation)'s genuine width/height swap for portrait, not just a rotation applied at the end. - db.py: widget_locked(), the widget-scoped equivalent of frame_locked() -- deliberately still locks at frame granularity (not a new per-widget lock) to avoid a new class of multi-lock deadlock bugs. - migration.py: _migration_16 creates the new tables; a separate _ensure_widgets_backfilled() (ORM-based, not raw SQL -- much less error-prone for this much per-mode branching) gives every existing frame a widget reproducing its exact current mode/settings, so upgrading changes nothing about what a frame displays or what its buttons do. calendar_photo_inlay frames specifically get two widgets (calendar + photo, split like the old inlay did) rather than silently losing the photo half. 10 new tests covering fresh-install backfill, re-run idempotency, the photo-inlay two-widget case, whiteboard's check_now button mapping, and migration_16's actual CREATE TABLE path against a simulated pre-existing database (not just the fresh-install create_all() shortcut). Full suite (69 tests) passes.