Move button actions to per-widget config, add hold-for-global-action

Next/back button assignment moves from a frame-level "Button
assignments" card into each widget's own gear-icon dialog, prefilled
with a sane default at creation (photos/calendar -> advance/back,
whiteboard/weather -> check_now, others -> none). At most one binding
per (widget, button) now -- cross-widget execution order never
mattered since each widget's action only touches its own state.

New firmware capability: holding NEXT or BACK past a configurable
duration (min 3s, server-side default) triggers a frame-wide action
instead of the per-widget short-press one -- cycling saved layouts,
refreshing all widgets, or freezing/unfreezing every photo widget (see
app/global_actions.py). Firmware next/back checks gain the same
hold-duration polling the combo button already had; the threshold
comes from the previous wake's /frame/config fetch (persisted in NVS),
since this wake's button decision happens before that request.

Not done here: firmware/version.txt is intentionally left unbumped --
this hasn't been built or hardware-tested (no ESP-IDF toolchain in this
environment), so no firmware release build should be triggered yet.

server/app/migration.py

@@ -24,7 +24,6 @@ from .models import (
     BatteryLog,
     CalendarWidgetConfig,
     Frame,
-    FrameButtonAction,
     FrameTaskList,
     PhotoWidgetConfig,
     ServerSettings,
@@ -32,6 +31,7 @@ from .models import (
     WhiteboardWidgetConfig,
     Widget,
 )
+from .widgets import default_button_actions
 
 logger = logging.getLogger(__name__)
 
@@ -725,6 +725,55 @@ def _migration_27(conn) -> None:
         conn.execute(text("ALTER TABLE photo_widget_configs ADD COLUMN locked INTEGER NOT NULL DEFAULT 0"))
 
 
+def _migration_28(conn) -> None:
+    """One action per (widget, button) instead of an ordered per-button
+    list -- button-action editing moved from the frame-level "Button
+    assignments" card into each widget's own config dialog (see
+    models.FrameButtonAction's updated docstring, routers/api_widgets.py's
+    api_widget_config_save). Cross-widget execution order never actually
+    mattered (each widget's action only touches its own state), so this
+    only needs to de-dupe down to one row before the new unique index can
+    be created -- MIN(id) per (widget_id, button) survives, arbitrarily
+    but deterministically, since which specific extra binding a user's
+    old list happened to have doesn't matter anymore."""
+    conn.execute(text(
+        "DELETE FROM frame_button_actions WHERE id NOT IN "
+        "(SELECT MIN(id) FROM frame_button_actions GROUP BY widget_id, button)"
+    ))
+    conn.execute(text(
+        "CREATE UNIQUE INDEX IF NOT EXISTS ix_frame_button_actions_widget_button "
+        "ON frame_button_actions (widget_id, button)"
+    ))
+
+
+def _migration_29(conn) -> None:
+    """Hold-for-global-action (see app/global_actions.py): holding NEXT/
+    BACK past hold_duration_ms triggers a frame-wide action instead of
+    the per-widget one a short press runs. next_hold_action/
+    back_hold_action are NULL (disabled) by default -- existing frames
+    get no new button behavior until someone opts in on the
+    Configuration tab. last_cycled_layout_id tracks where a repeated
+    "cycle saved layouts" hold should resume from.
+
+    Guarded per-column, same reasoning as migration 26/27's own
+    comments: frames is a table test_migrations.py's pre-widget-system
+    replay tests leave un-dropped (unlike calendar/task/widget tables
+    those tests DROP and recreate in an old shape), so it keeps the
+    fresh-install create_all() copy -- which already has these columns
+    -- when those tests replay migrations 17+ from schema_version 16.
+    Without the guard, replaying this migration there re-adds a column
+    that's already there and SQLite raises "duplicate column name"."""
+    existing = {c["name"] for c in inspect(conn).get_columns("frames")}
+    if "hold_duration_ms" not in existing:
+        conn.execute(text("ALTER TABLE frames ADD COLUMN hold_duration_ms INTEGER NOT NULL DEFAULT 3000"))
+    if "next_hold_action" not in existing:
+        conn.execute(text("ALTER TABLE frames ADD COLUMN next_hold_action TEXT"))
+    if "back_hold_action" not in existing:
+        conn.execute(text("ALTER TABLE frames ADD COLUMN back_hold_action TEXT"))
+    if "last_cycled_layout_id" not in existing:
+        conn.execute(text("ALTER TABLE frames ADD COLUMN last_cycled_layout_id INTEGER"))
+
+
 MIGRATIONS = [
     (1, _migration_1),
     (2, _migration_2),
@@ -753,6 +802,8 @@ MIGRATIONS = [
     (25, _migration_25),
     (26, _migration_26),
     (27, _migration_27),
+    (28, _migration_28),
+    (29, _migration_29),
 ]
 
 
@@ -963,26 +1014,6 @@ def _whiteboard_config_from_frame(frame: Frame, widget_id: int) -> WhiteboardWid
     )
 
 
-def _default_button_actions(frame_id: int, widget_id: int, widget_type: str) -> list[FrameButtonAction]:
-    """NEXT/BACK -> whatever this widget's own advance/back concept is
-    (see app/widgets/ for the actual action registry, built in a later
-    phase) -- reproduces each mode's exact old button behavior for the
-    one auto-migrated widget, so upgrading changes nothing about what the
-    physical buttons do until someone deliberately reassigns them."""
-    if widget_type == "whiteboard":
-        # No real "next"/"back" concept for a static board -- both
-        # buttons already meant "check now" before this migration (see
-        # the old _advance_whiteboard_mode/_back_whiteboard_mode).
-        return [
-            FrameButtonAction(frame_id=frame_id, button="next", widget_id=widget_id, action="check_now"),
-            FrameButtonAction(frame_id=frame_id, button="back", widget_id=widget_id, action="check_now"),
-        ]
-    return [
-        FrameButtonAction(frame_id=frame_id, button="next", widget_id=widget_id, action="advance"),
-        FrameButtonAction(frame_id=frame_id, button="back", widget_id=widget_id, action="back"),
-    ]
-
-
 def _maybe_add_legacy_tasks_widget(db, frame: Frame, existing: list[grid.Rect], next_sort_order: int) -> None:
     """Only relevant for a database jumping straight from before the
     widget system existed to after tasks became their own widget type
@@ -1032,7 +1063,7 @@ def _backfill_frame_widgets(db, frame: Frame) -> None:
         db.flush()  # assign ids before the FK'd config rows reference them
         db.add(_calendar_config_from_frame(frame, cal_widget.id))
         db.add(_photo_config_from_frame(frame, photo_widget.id))
-        db.add_all(_default_button_actions(frame.id, cal_widget.id, "calendar"))
+        db.add_all(default_button_actions(frame.id, cal_widget.id, "calendar"))
         _maybe_add_legacy_tasks_widget(
             db, frame, [(0, 0, cols - half, rows), (cols - half, 0, half, rows)], next_sort_order=2
         )
@@ -1048,7 +1079,7 @@ def _backfill_frame_widgets(db, frame: Frame) -> None:
         db.add(_calendar_config_from_frame(frame, widget.id))
     elif mode == "whiteboard":
         db.add(_whiteboard_config_from_frame(frame, widget.id))
-    db.add_all(_default_button_actions(frame.id, widget.id, mode))
+    db.add_all(default_button_actions(frame.id, widget.id, mode))
     if mode == "calendar":
         _maybe_add_legacy_tasks_widget(db, frame, [(0, 0, cols, rows)], next_sort_order=1)