Make hotel name configurable via VITE_HOTEL_NAME build arg

Defaults to 'Number Four at Stow'. Replaces hardcoded 'Hotel Number Four'
and 'HNF Manage' in sidebar, login page, and browser title. Other hotels
set VITE_HOTEL_NAME in their /opt/portal/.env before rebuilding.

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

docker-compose.yml

@@ -1,6 +1,9 @@
 services:
   portal:
-    build: .
+    build:
+      context: .
+      args:
+        VITE_HOTEL_NAME: ${VITE_HOTEL_NAME:-Number Four at Stow}
     security_opt:
       - apparmor=unconfined
     ports: