feat(ui): consolidate map filters and rework station selection

- replace inline filter pills with a single "Filters" popover containing
  small pill buttons for fuel/radius/sort/brand (no native <select>s)
- map polish: Carto Positron tiles, hidden zoom buttons, locate-me floating
  button + accuracy ring, smooth flyTo transitions, slim ⓘ attribution
- map markers no longer open Leaflet popups; clicking a marker selects the
  station and surfaces the existing StationCard inline over the map, with
  swipe-down-to-close and a small overlay × button
- price colour now reflects deal quality (cheap / average / expensive vs
  search avg ± 3p) on both list and map — stable across sort/filter
- promote the "X ago" timestamp into the card header so it stays visible
  in the expanded state

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

resources/css/app.css

@@ -16,6 +16,14 @@
     .pill.is-active {
         @apply bg-primary/10 border-primary text-primary;
     }
+
+    .pill-sm {
+        @apply relative inline-flex items-center justify-center gap-1 h-8 px-2.5 rounded-full border bg-white border-zinc-200 text-zinc-700 text-xs font-medium transition-colors cursor-pointer hover:border-zinc-300;
+    }
+
+    .pill-sm.is-active {
+        @apply bg-primary/10 border-primary text-primary;
+    }
 }
 
 @theme {