Add standalone weather widget (current/hourly/daily/multi-city, pluggable providers)

New widget type with four display modes -- current conditions, an
hourly forecast strip, a multi-day forecast, and several cities' current
day side by side -- backed by a pluggable provider registry (app/weather/,
mirroring the app/widgets/ dispatch pattern): Open-Meteo (worldwide) and
NWS (US-only) both wired up now, Environment Canada documented as the
next one to add given its more involved station/grid-lookup API.

The calendar widget's existing embedded weather strip is untouched and
still Open-Meteo-only; this lifts the same underlying icon-drawing
primitives (now shared via app/weather_render.py, calendar_render.py
still imports draw_weather_row unchanged) into a widget that can be
placed and sized on its own. Icons are redrawn in the panel's actual ink
colors (yellow sun/bolt, blue rain/snow) instead of flat black, and
build_multi_city's icon/font sizing now scales with how many cities need
to fit rather than the box's height alone -- both fixed after catching
them via live browser verification, along with a mode-switch cache-shape
crash and a mobile-width dialog overflow.

New WeatherWidgetConfig table (migration 24), grid footprint, widget
module, common.py fetch/cache helper, router endpoints (location set/
clear, city add/remove, preview), dialog template + JS, and full test
coverage (providers, widget render, HTTP endpoints, migration replay).
docs/widgets.md and CLAUDE.md's TODO updated accordingly.

server/app/migration.py

@@ -624,6 +624,38 @@ def _migration_23(conn) -> None:
     ))
 
 
+def _migration_24(conn) -> None:
+    """New widget type: standalone weather (current/hourly/daily/
+    multi_city display modes, pluggable Open-Meteo/NWS providers -- see
+    models.WeatherWidgetConfig, app/weather/, app/widgets/weather.py).
+    Lifts the calendar widget's embedded weather strip's underlying
+    fetch/render building blocks (app/weather/open_meteo.py, the icon-
+    drawing primitives now in app/weather_render.py) out into a widget
+    that can be placed/sized on its own -- CalendarWidgetConfig's own
+    weather_* columns are untouched, still working exactly as before.
+
+    Raw CREATE TABLE, not Base.metadata.create_all, same reasoning as
+    migration 20/21/23's own comments: create_all always reflects
+    models.py's CURRENT shape, so replaying the full chain on an old
+    database could collide with a later migration's ALTER TABLE on this
+    same table."""
+    conn.execute(text(
+        "CREATE TABLE weather_widget_configs ("
+        "widget_id INTEGER PRIMARY KEY REFERENCES widgets(id) ON DELETE CASCADE, "
+        "mode TEXT NOT NULL DEFAULT 'current', "
+        "provider TEXT NOT NULL DEFAULT 'open_meteo', "
+        "units TEXT NOT NULL DEFAULT 'fahrenheit', "
+        "city_label TEXT, "
+        "city_latitude REAL, "
+        "city_longitude REAL, "
+        "hourly_interval_hours INTEGER NOT NULL DEFAULT 4, "
+        "daily_days INTEGER NOT NULL DEFAULT 5, "
+        "cities TEXT, "
+        "checked_at REAL NOT NULL DEFAULT 0.0, "
+        "cached TEXT)"
+    ))
+
+
 MIGRATIONS = [
     (1, _migration_1),
     (2, _migration_2),
@@ -648,6 +680,7 @@ MIGRATIONS = [
     (21, _migration_21),
     (22, _migration_22),
     (23, _migration_23),
+    (24, _migration_24),
 ]