feat(hikes): worldwide maps via a region-switching tile proxy

Add tile-proxy/: a small Rust (axum) service behind nginx that serves one
canonical XYZ scheme (/{karte,luftbild,dufour}/{z}/{x}/{y}) and, per tile,
picks the provider by geometry — swisstopo when the tile overlaps a
swisstopo-covered region (Switzerland or Liechtenstein, each simplified +
2 km buffer; tile-bbox ∩ polygon at every zoom), otherwise OpenTopoMap
(schematic) / Esri World Imagery (satellite), with an auto-fallback for
border 404s. Includes the region generator (gen-regions.mjs), a Makefile,
nginx caching-proxy + systemd examples, and a README. Listen address is
env-driven (TILE_PROXY_ADDR).

App side:
- New mapTiles.ts is the single source for the proxy URLs + combined
  attribution; HikeMap / HikesOverviewMap / EditMap fetch through
  maps.bocken.org instead of swisstopo directly, on-map attribution
  controls removed, preconnect + footer credits updated (swisstopo /
  OpenStreetMap+OpenTopoMap / Esri).
- Region-aware schematic max zoom (isSwissRegion helper): detail map caps
  at z17 abroad and hides the CH/LI-only Dufour layer; overview caps at
  z18 when a shown hike is abroad.
- Route-builder: add the satellite layer via the same bottom-right layer
  popover as the other maps.

src/routes/hikes/+page.svelte

@@ -253,9 +253,12 @@
 		     credit to appear somewhere on the page. -->
 		<footer class="map-credit">
 			Kartendaten &copy;
-			<a href="https://www.swisstopo.admin.ch/" target="_blank" rel="noopener noreferrer">
-				swisstopo
-			</a>
+			<a href="https://www.swisstopo.admin.ch/" target="_blank" rel="noopener noreferrer">swisstopo</a>
+			·
+			<a href="https://www.openstreetmap.org/copyright" target="_blank" rel="noopener noreferrer">OpenStreetMap</a>,
+			<a href="https://opentopomap.org/" target="_blank" rel="noopener noreferrer">OpenTopoMap</a>
+			·
+			<a href="https://www.esri.com/" target="_blank" rel="noopener noreferrer">Esri</a>
 		</footer>
 	</div>
 </section>