Add wiki link rewriting to local Kiwix

Rewrites OSM wikipedia/wikidata/wikivoyage/appropedia extratag values
to local Kiwix URLs (wiki.echo6.co) when the article exists in a loaded
ZIM, falling back silently to public URLs otherwise.

- New lib/wiki_rewrite.py: URL classification, Kiwix OPDS catalog
  discovery (xml.etree.ElementTree), HEAD-based availability check,
  positive-only SQLite cache, disabled discovery stubs
- place_detail.py: _enrich_wiki_links() at both Nominatim and Overpass
  enrichment sites, before cache_put
- Profile flags: has_wiki_rewriting (home/regional: true, minimal: false),
  has_wiki_discovery (all: false, stubs for future activation)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

config/profiles/home.yaml

@@ -38,10 +38,13 @@ features:
   has_3d_terrain: false
   has_traffic_overlay: true
   has_landclass: true
+  has_public_lands_layer: true
   has_address_book_write: false
   has_overture_enrichment: true
   has_google_places_enrichment: true
   has_contacts: true
+  has_wiki_rewriting: true
+  has_wiki_discovery: false
 
 defaults:
   center: [42.5736, -114.6066]