Add Environment Canada as a third weather provider

app/weather/ec.py -- api.weather.gc.ca's MSC GeoMet OGC API
(citypageweather-realtime collection), the modern replacement for the
old dd.weatheroffice.gc.ca XML feed (that host no longer resolves).
Unlike Open-Meteo/NWS's simple lat/lon REST, this collection is only
queryable by bounding box, so _nearest_site widens the box
progressively and picks the closest of the ~844 sites by straight-line
distance -- capped at 300km, calibrated against a real bug caught in
development where an unconditional "nearest site, however far" matched
a Miami, FL query to a site in Ontario 1824km away once the box widened
to cover the whole country.

EC's own numeric icon codes get a small confirmed-against-live-data
mapping table plus the same keyword-on-condition-text fallback NWS
already uses for anything unmapped. Daily periods are named ("Today"/
"Tonight"/"Tuesday"/...) rather than dated, so dates are inferred by
walking them in issued order.

Verified end-to-end against the real live API (Toronto, rural
Saskatchewan, a US border city, and a rejected far-away match) and
through the browser (daily mode, composited panel preview). Test
fixtures mirror the actual response shapes captured live. docs/
widgets.md and CLAUDE.md's TODO updated -- EC is no longer a documented
gap.

CLAUDE.md

@@ -9,7 +9,6 @@ photos/calendar/whiteboard/weather widget system to the device.
 CURRENT TODO
 -add more actions for buttons (i.e. change widget/layout)
 -Fix spurious button assignment stuff (probably but buttons on widget config with sane defaults)
--add Environment Canada as a weather widget provider (app/weather/ -- station/grid-lookup API, more involved than Open-Meteo/NWS)
 -widget border option
 -battery life widget
 -sharing layouts with linked users