Add npm run dev:lan for phone testing over the LAN

Adds a dev:lan script (vite --host) so testing on a real device doesn't
require permanently changing vite.config.ts's default 127.0.0.1-only
binding. Pairs with a small supabaseClient change: when the configured
Supabase URL is local (127.0.0.1/localhost), the client now swaps in
whatever hostname the page itself was loaded from, so a phone hitting the
dev server's LAN IP gets API calls routed to that same IP automatically —
no more hand-editing VITE_SUPABASE_URL per network. Never touches a real
production Supabase URL.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017DUU6CnxECCDeqDNYJgr5x

package.json

@@ -5,6 +5,7 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
+    "dev:lan": "vite --host",
     "build": "tsc -b && vite build",
     "lint": "oxlint",
     "preview": "vite preview",