Split the tasks feature out of the calendar widget into its own widget type

Task lists used to be a week-view-only sub-feature bolted onto calendar
widgets (CalendarWidgetConfig.tasks_*), so a task list could only exist
tied to a calendar's view and only inside its footprint. Tasks are now
a standalone widget type (TaskWidgetConfig, app/widgets/tasks.py) that
can be placed and sized independently, same as photos/calendar/
whiteboard -- no separate "enabled" flag either, since being on the
grid at all is the on/off switch, matching every other widget type.

Migration 17 creates task_widget_configs, extracts any existing
calendar widget's configured task source into a new sibling tasks
widget (auto-placed in open grid space, source dropped+logged if truly
none is left), then drops calendar_widget_configs' now-dead tasks_*
columns in the same migration -- this project's usual same-migration-
drop convention. Also handles the rarer case of a database jumping
straight from before the widget system existed to after this split in
one boot, via the legacy Frame.calendar_tasks_* columns.

Verified live in the browser at desktop and mobile widths: adding a
Tasks widget, its own dialog (task-list source picker + preview), and
confirming the calendar widget's dialog no longer mentions tasks at
all. Full test suite (180 tests, including new coverage for the widget
render/actions, the migration's data-extraction path, and the
permission-boundary shape for tasks-source) passes.

server/app/widgets/__init__.py

@@ -36,10 +36,11 @@ Each module in this package exposes:
 
 from __future__ import annotations
 
-from . import calendar, photos, whiteboard
+from . import calendar, photos, tasks, whiteboard
 
 WIDGET_TYPES = {
     "photos": photos,
     "calendar": calendar,
     "whiteboard": whiteboard,
+    "tasks": tasks,
 }

server/app/widgets/calendar.py

@@ -24,7 +24,6 @@ from ..db import widget_locked
 from ..models import CalendarWidgetConfig, Frame, Widget
 from ..routers.common import (
     get_or_refresh_calendar_events_for_widget,
-    get_or_refresh_tasks_for_widget,
     get_or_refresh_weather_for_widget,
 )
 
@@ -47,16 +46,12 @@ def render(db: Session, frame: Frame, widget: Widget, target_w: int, target_h: i
     cfg = db.get(CalendarWidgetConfig, widget.id)
     events, fetch_summary = get_or_refresh_calendar_events_for_widget(db, frame, widget)
     weather_cities = get_or_refresh_weather_for_widget(db, frame, widget) if cfg.weather_enabled else None
-    tasks = (
-        get_or_refresh_tasks_for_widget(db, frame, widget)
-        if (cfg.view == "week" and cfg.tasks_enabled) else None
-    )
 
     return _build(
         events, view=cfg.view, browse_offset=cfg.browse_offset, target_w=target_w, target_h=target_h,
         timezone=frame.timezone, fetch_summary=fetch_summary, week_start=cfg.week_start,
         palette_rgb=frame.palette_rgb, weather_cities=weather_cities, weather_units=cfg.weather_units,
-        week_days=cfg.week_days, week_layout=cfg.week_layout, tasks=tasks,
+        week_days=cfg.week_days, week_layout=cfg.week_layout,
         week_start_offset=cfg.week_start_offset,
     )
 

server/app/widgets/tasks.py

@@ -0,0 +1,36 @@
+"""Tasks widget: a simple outstanding-task checklist in its own region --
+split out of the calendar widget's old week-view-only task list (see
+models.TaskWidgetConfig) so a task list can be placed and sized on its
+own, independent of any calendar's view/footprint.
+
+No "enabled" concept and no button actions: the widget's mere presence
+on the grid is the on/off switch (same as every other widget type), and
+its cache refreshes on the same throttled schedule as weather -- nothing
+here to advance/back/force."""
+
+from __future__ import annotations
+
+from PIL import Image
+from sqlalchemy.orm import Session
+
+from ..calendar_render import _build_tasks
+from ..models import Frame, TaskWidgetConfig, Widget
+from ..routers.common import get_or_refresh_tasks_for_widget
+from ._shared import placeholder_image
+
+ACTION_LABELS: dict[str, str] = {}
+
+
+def render(db: Session, frame: Frame, widget: Widget, target_w: int, target_h: int,
+          is_normal_wake: bool = True) -> Image.Image:
+    """is_normal_wake is unused here -- see app/widgets/photos.py's
+    identical note; every widget type's render() shares one call
+    signature regardless of which ones actually care."""
+    cfg = db.get(TaskWidgetConfig, widget.id)
+    if not cfg.calendar_key or not cfg.user_id:
+        return placeholder_image(target_w, target_h, ["Tasks widget", "not configured yet"])
+    tasks = get_or_refresh_tasks_for_widget(db, frame, widget)
+    return _build_tasks(tasks, target_w, target_h)
+
+
+ACTIONS: dict = {}