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/routers/frame_pages.py

@@ -21,6 +21,7 @@ from .. import weather
 from ..auth import can_view_frame, current_user
 from ..calendar_render import CALENDAR_VIEW_LABELS
 from ..db import get_db
+from ..global_actions import GLOBAL_ACTION_LABELS
 from ..image_pipeline import (
     BORDER_STYLES,
     BORDER_STYLE_LABELS,
@@ -36,6 +37,7 @@ from ..models import (
     BatteryWidgetConfig,
     CalendarWidgetConfig,
     Frame,
+    FrameButtonAction,
     FrameCalendar,
     FrameTaskList,
     PhotoWidgetConfig,
@@ -49,6 +51,7 @@ from ..models import (
     Widget,
 )
 from ..quiet_hours import ALL_TIMEZONES
+from ..widgets import WIDGET_TYPES
 from ..widgets import text as text_widget
 from .common import shell_context, widget_of_type
 
@@ -88,6 +91,7 @@ def frame_config_page(frame_id: int, request: Request, db: Session = Depends(get
         default_palette_rgb=DEFAULT_PALETTE_RGB,
         palette_to_hex=palette_to_hex,
         photo_widget_id=photo_widget_id,
+        global_action_labels=GLOBAL_ACTION_LABELS,
     )
 
 
@@ -232,11 +236,30 @@ def widget_dialog(frame_id: int, widget_id: int, request: Request, db: Session =
         "max_border_thickness": MAX_BORDER_THICKNESS,
     }
 
+    # Every dialog also includes the shared "Button actions" card
+    # (_widget_button_fields.html) if this widget type supports any --
+    # empty for tasks/static/text/battery, so the card renders nothing
+    # for those. Bindings, not the type's own config, so this lives in
+    # FrameButtonAction (see models.py), same reasoning as border_ctx
+    # above for why it's a separate card/endpoint from the type-specific
+    # form.
+    bindings = {
+        row.button: row.action
+        for row in db.scalars(
+            select(FrameButtonAction).where(FrameButtonAction.widget_id == widget.id)
+        )
+    }
+    button_ctx = {
+        "button_action_labels": WIDGET_TYPES[widget.widget_type].ACTION_LABELS,
+        "next_button_action": bindings.get("next", ""),
+        "back_button_action": bindings.get("back", ""),
+    }
+
     if widget.widget_type == "photos":
         photo_cfg = db.get(PhotoWidgetConfig, widget.id)
         return templates.TemplateResponse("_widget_dialog_photos.html", {
             "request": request, "frame": frame, "widget": widget, "photo_cfg": photo_cfg,
-            "display_mode_labels": DISPLAY_MODE_LABELS, **border_ctx,
+            "display_mode_labels": DISPLAY_MODE_LABELS, **border_ctx, **button_ctx,
         })
 
     if widget.widget_type == "calendar":
@@ -247,7 +270,7 @@ def widget_dialog(frame_id: int, widget_id: int, request: Request, db: Session =
             "calendar_users": _calendar_users_for_widget(db, frame.id, widget.id, user.id),
             "week_start_labels": WEEK_START_LABELS,
             "calendar_color_labels": PALETTE_LABELS,
-            **border_ctx,
+            **border_ctx, **button_ctx,
         })
 
     if widget.widget_type == "tasks":
@@ -256,7 +279,7 @@ def widget_dialog(frame_id: int, widget_id: int, request: Request, db: Session =
             "request": request, "frame": frame, "widget": widget, "task_cfg": task_cfg, "user": user,
             "task_users": _task_users_for_widget(db, frame.id, widget.id, user.id),
             "task_color_labels": PALETTE_LABELS,
-            **border_ctx,
+            **border_ctx, **button_ctx,
         })
 
     if widget.widget_type == "static":
@@ -264,14 +287,14 @@ def widget_dialog(frame_id: int, widget_id: int, request: Request, db: Session =
         return templates.TemplateResponse("_widget_dialog_static.html", {
             "request": request, "frame": frame, "widget": widget, "static_cfg": static_cfg,
             "display_mode_labels": {k: v for k, v in DISPLAY_MODE_LABELS.items() if k in STATIC_DISPLAY_MODES},
-            **border_ctx,
+            **border_ctx, **button_ctx,
         })
 
     if widget.widget_type == "text":
         text_cfg = db.get(TextWidgetConfig, widget.id)
         return templates.TemplateResponse("_widget_dialog_text.html", {
             "request": request, "frame": frame, "widget": widget, "text_cfg": text_cfg,
-            "text_font_families": text_widget.FONT_FAMILIES, **border_ctx,
+            "text_font_families": text_widget.FONT_FAMILIES, **border_ctx, **button_ctx,
         })
 
     if widget.widget_type == "whiteboard":
@@ -282,20 +305,20 @@ def widget_dialog(frame_id: int, widget_id: int, request: Request, db: Session =
         return templates.TemplateResponse("_widget_dialog_whiteboard.html", {
             "request": request, "frame": frame, "widget": widget, "user": user,
             "whiteboard_source": _whiteboard_source_info(db, whiteboard_cfg),
-            "viewer_has_webdav_creds": viewer_has_webdav_creds, **border_ctx,
+            "viewer_has_webdav_creds": viewer_has_webdav_creds, **border_ctx, **button_ctx,
         })
 
     if widget.widget_type == "weather":
         weather_cfg = db.get(WeatherWidgetConfig, widget.id)
         return templates.TemplateResponse("_widget_dialog_weather.html", {
             "request": request, "frame": frame, "widget": widget, "weather_cfg": weather_cfg,
-            "weather_provider_labels": weather.PROVIDER_LABELS, **border_ctx,
+            "weather_provider_labels": weather.PROVIDER_LABELS, **border_ctx, **button_ctx,
         })
 
     if widget.widget_type == "battery":
         battery_cfg = db.get(BatteryWidgetConfig, widget.id)
         return templates.TemplateResponse("_widget_dialog_battery.html", {
-            "request": request, "frame": frame, "widget": widget, "battery_cfg": battery_cfg, **border_ctx,
+            "request": request, "frame": frame, "widget": widget, "battery_cfg": battery_cfg, **border_ctx, **button_ctx,
         })
 
     raise HTTPException(400, f"Unknown widget type: {widget.widget_type}")