feat(roadtrip): tell petrol from electric, and shape the refuel band like a drive band

Four things that only showed up once it was on screen.

The range budget treated a petrol station and a charger as the same thing, so an electric
car pausing for coffee at a filling station had its battery refilled on paper: the
warnings went quiet for the rest of the day and the driver was told nothing. A vehicle can
now be named, and then only what actually refills it counts — and the search asks for that
kind alone instead of offering pumps to a car that cannot use them. Not saying keeps the
old behaviour, which is what everybody who never opens the dialog is on.

The band was its own shape in a rail made of drive bands. It is one now: the same rail,
the same height, the same type size, a warning tint instead of a ring, and the figures
where a drive band keeps them. The buttons are icons of the same 18px square the shuffle
mark uses, so the band stays one line beside its neighbours.

The old range warning stood down where the band shows. Both at once said the same thing
twice in the wrong order — the answer above the problem — because the warning marks the
stop somebody finds out at while the band sits on the leg the fuel ends on.

Two measured corrections to the search itself. The server turns a box into a circle of
half its diagonal and silently narrows anything past 20 km, so a box of ±25 asked for 35
and came back flagged as narrowed EVERY time, which read on screen as "we could not
check"; ±14 asks for 19.8 and is answered in full. And the circle is centred 12 km before
the dry point rather than on it, because only road already driven is any use — centred on
the point, half the circle was spent on road nobody can reach.

An answer that finds nothing now leaves the button rather than only a close. The place
search is a shared public service that does time out, and "it did not answer" with no way
to ask again reads as broken rather than as busy.

client/src/types.ts

@@ -159,6 +159,14 @@ export interface Settings {
    * because it goes to the router as one request either way.
    */
   roadtrip_avoid?: string
+  /**
+   * What the traveller drives: 'combustion', 'electric', or absent for "did not say".
+   *
+   * Absent has to mean BOTH kinds refill, which is what the range budget did before this
+   * existed. Anything else would quietly change the warnings of every traveller who never
+   * opened the dialog.
+   */
+  roadtrip_vehicle?: string
   /** CARTO basemaps watermark keyless tiles; the key is appended as ?key= (#2054). */
   carto_api_key?: string
   mapbox_access_token?: string