[public-store-distance] Consume the public distance contract, stop labelling it as unavailable

Guest browsing showed 'Distância indisponível' on every store card and a
'--' tile on store detail, because the public locator response carries no
distance and StoreSummary.init(publicItem:) hardcoded nil.

Backend contract (docs/plans/public-store-distance-consumer.md): distance
is a number, never null, 0 means unavailable. Implemented app-side ahead of
the backend - every change is forward-compatible, and the part that removes
the broken label works with no backend at all.

- PublicStoreListItem / PublicStoreDetail: + distance (optional, so today's
  responses without the field still decode).
- StoreSummary.init(publicItem:): normalize the 0 sentinel to nil, so one
  representation of 'unknown' reaches the label and the max-distance filter.
- fetchStoreDetail: send state/city from GuestLocationStore by default -
  the server needs them to resolve the city centroid.
- formatDistance: empty string for nil/0/negative. It previously returned
  'Distância indisponível' for nil, and - found by the new test - '0 m' for
  0 and '-1000 m' for a negative.
- StoreCard: drop the distance segment and its '·' separator together,
  otherwise the row ended in a dangling separator.
- StoreDetailView: drop the DISTÂNCIA tile and its divider instead of '--'.

Also fixes the same label in the authenticated flow when the user declined
location and has no address coordinates.

Tests: PublicStoreDistanceTests (decode with/without the field, passthrough,
0 normalization) + the empty case in HomeViewFilteringTests.

PediFoodsTests/HomeViewFilteringTests.swift

@@ -63,5 +63,17 @@ func formatDistanceSwitchesUnitsAtOneKm() {
     #expect(view.formatDistance(0.5) == "500 m")
     #expect(view.formatDistance(1.0) == "1.0 km")
     #expect(view.formatDistance(2.3) == "2.3 km")
-    #expect(view.formatDistance(nil) == "Distância indisponível")
+}
+
+/// Contract (docs/plans/public-store-distance-consumer.md): the API never
+/// sends null - `0` means "no distance available". Both that and a missing
+/// value render as an empty string so the caller omits the segment
+/// entirely, instead of showing "Distância indisponível" or "0 m".
+@Test("formatDistance renders nothing when the distance is missing or zero")
+@MainActor
+func formatDistanceIsEmptyWhenUnavailable() {
+    let view = makeHomeView()
+    #expect(view.formatDistance(nil) == "")
+    #expect(view.formatDistance(0) == "")
+    #expect(view.formatDistance(-1) == "")
 }