fix(auth): route server-side Supabase calls via internal URL to avoid edge rate-limit

Server-side Supabase calls (middleware getUser/refresh, server components,
admin client) all egress through the Docker gateway as a single NATed IP and
traverse Caddy's per-IP /auth/* rate limiter (8 events/s). A handful of active
users saturate that shared bucket, 429ing getUser()/token refresh; the
middleware then treats the session as invalid and bounces to /login, while a
manual refresh lands under budget and works again.

Add SUPABASE_INTERNAL_URL (e.g. http://kong-prod:8000) used only by the
server-side clients (middleware, lib/supabase/server.ts, admin getSupabaseAdmin
/getSupabaseAnon), falling back to the public URL when unset. Browser clients
keep the public URL so real per-user-IP edge rate limiting still applies.

Also bake the arg in the Dockerfile/build and make the web-prod network alias
durable via WEB_ALIAS (dev sets web-dev) so the dev container can't reclaim the
web-prod alias on redeploy.

middleware.ts

@@ -25,7 +25,13 @@ export async function middleware(request: NextRequest) {
   let response = NextResponse.next({ request });
 
   const supabase = createServerClient(
-    process.env.NEXT_PUBLIC_SUPABASE_URL!,
+    // Server-side requests reach Supabase directly over the Docker network
+    // (SUPABASE_INTERNAL_URL, e.g. http://kong-prod:8000) so they bypass
+    // Caddy's per-IP `/auth/*` rate limiter; all server traffic would
+    // otherwise share a single NATed gateway IP and saturate that budget,
+    // intermittently 429ing getUser() and bouncing users to /login. Falls
+    // back to the public URL when the internal one is not configured.
+    process.env.SUPABASE_INTERNAL_URL ?? process.env.NEXT_PUBLIC_SUPABASE_URL!,
     process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
     {
       cookies: {