feat(hikes): redesign /hikes filter as a quiet command bar

Replace the flat always-open filter slab with a collapsed command bar:
a result/totals summary, removable active-filter chips, and a Filter
toggle (with active-count badge). The control panel expands in-flow
below the bar (slide), pushing the card grid down instead of overlaying
it, with breathing room added between the hero map and the bar.

- Range filters are now dual-thumb sliders (lower + upper bound) for
  distance, duration, ascent and descent, via a new RangeSlider
  component (pointer + keyboard, crossover hand-off). Shared bounds math
  lives in filterBounds.ts so slider extents and the page's default
  filter state can't drift.
- Difficulty selection renders the actual SAC trail-sign markers
  (T1 yellow Wegweiser, T2/T3 white-red-white, T4-T6 white-blue-white),
  matching the hike cards; selected signs light up in full colour while
  unselected ones are dimmed.
- Tag selection uses a typeahead (input + dropdown + removable chips),
  mirroring the recipe filter but themed with the semantic variables.

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "homepage",
-	"version": "1.77.2",
+	"version": "1.78.0",
 	"private": true,
 	"type": "module",
 	"scripts": {