feat(navi): deployment profiles + /api/config endpoint

Add profile-driven config infrastructure:
- config/profiles/{home,regional_pi,minimal_pi}.yaml templates
- lib/deployment_config.py loader (reads RECON_PROFILE env var)
- GET /api/config returns active profile as JSON (5min cache)

Frontend reads this on startup to determine tile source, defaults,
and feature flags. No existing behavior changed.

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

config/profiles/regional_pi.yaml

@@ -0,0 +1,31 @@
+# Deployment profile: Regional Pi (multi-state field kit)
+# Template for a Raspberry Pi covering Idaho + surrounding states.
+# Override via RECON_PROFILE env var.
+
+profile: regional_pi
+region_name: "Idaho + Neighbors"
+
+tileset:
+  url: "/tiles/regional.pmtiles"
+  bounds: [-125, 40, -104, 49]
+  max_zoom: 15
+  attribution: "Protomaps © OSM"
+
+services:
+  geocode: "/api/geocode"
+  reverse: "/api/reverse"
+  address_book: "/api/address_book"
+  valhalla: "/valhalla"
+
+features:
+  has_nominatim_details: false
+  has_kiwix_wiki: false
+  has_hillshade: true
+  has_3d_terrain: false
+  has_traffic_overlay: false
+  has_landclass: true
+  has_address_book_write: true
+
+defaults:
+  center: [44.0, -114.0]
+  zoom: 7