feat(roadtrip): remember which track a day follows

The vias already made the day follow the road; nothing said which road. After a
reload the badge could only say "shaped by hand", and re-fitting after the stops
changed meant finding the track again by eye.

One row per day, written in the same transaction as the chain it describes: a
day claiming to follow a road whose vias never landed would be worse than a day
claiming nothing. Three states rather than two, which is why the field is an
object and not an id — absent leaves whatever the day followed alone, null says
it follows nothing, an object records the road it now takes. A bare nullable id
could not tell "do not touch this" apart from "forget it", and a hand-dragged
via on the same day must not wipe the label.

The foreign key is the point: delete the imported track and the label cascades
with it, so no day is left claiming to follow a line nobody can see. The vias
stay, because they are the drive.

Both write paths check that the place is a track of this trip before it becomes
a label — permission alone would let another trip's place id, or an ordinary
place, become a name that can never be drawn.

Also clears three reliability findings the scanner raised on this branch: two
default sorts given an explicit comparator, and a trailing-slash regex the
scanner is right to call backtracking, walked instead.

client/src/components/Map/RouteCalculator.ts

@@ -31,10 +31,23 @@ const OSRM_PROFILE_PATH: Record<'driving' | 'walking' | 'cycling', string> = {
  * A configured base is expected to serve the standard OSRM layout,
  * `<base>/route/v1/<profile>/…`, which is what `osrm-routed` does out of the box.
  */
+/**
+ * A configured base URL without its trailing slashes.
+ *
+ * Walked rather than matched with `/\/+$/`: that pattern backtracks over a run of
+ * slashes, and the value comes from an instance setting somebody types. Linear either
+ * way in practice, but the regex is the shape a scanner is right to flag.
+ */
+function withoutTrailingSlashes(value: string): string {
+  let end = value.length
+  while (end > 0 && value[end - 1] === '/') end -= 1
+  return value.slice(0, end)
+}
+
 function routeBaseFor(profile: 'driving' | 'walking' | 'cycling'): string {
   const configured = useSettingsStore.getState().settings.routing_base_url?.trim()
   if (!configured) return OSRM_PROFILE_BASE[profile]
-  return `${configured.replace(/\/+$/, '')}/route/v1/${OSRM_PROFILE_PATH[profile]}`
+  return `${withoutTrailingSlashes(configured)}/route/v1/${OSRM_PROFILE_PATH[profile]}`
 }
 
 /**