The widget previously read stations only from the app-group cache, which
SideStore free accounts don't provision — the widget process saw empty
data and silently fell back to sample stations (stuck on Morrisons).
Now the widget makes its own focused relay fetch around its location
(radius + limit 500, 5s timeout) whenever it has a fix, falling back to
the shared cache then samples. Widget data now reflects the relay
independently of the app. 35 tests pass.