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.

tile-proxy/Makefile

@@ -0,0 +1,20 @@
+BIN := tile-proxy
+
+.PHONY: build run regions clean
+
+# Build release binary and drop it in ./ (next to this Makefile).
+build:
+	cargo build --release
+	cp target/release/$(BIN) ./$(BIN)
+
+# Build, then run (override the port with TILE_PROXY_ADDR=...).
+run: build
+	./$(BIN)
+
+# Regenerate the swisstopo-region polygons CH + LI (src/regions.in).
+regions:
+	node scripts/gen-regions.mjs
+
+clean:
+	cargo clean
+	rm -f ./$(BIN)