refactor: remove hotel-name fallback, fail fast when unconfigured

Drop the hardcoded FALLBACK_HOTEL_NAME ("Atom") preset and the brand.ts
module. HOTEL_NAME is now a required env var: if it (and the CMS hotel_name
setting) is missing the site fails validation at startup/build with a clear
message instead of silently rendering a placeholder hotel name.

resolveHotelName() resolves CMS hotel_name -> required HOTEL_NAME only.
Callers that used the preset (api/home route catch branch, CMS settings form
default, mobile-nav/logo-generator prop defaults) now use the configured name
or an empty default; the real name is already passed in by server parents.

src/lib/hotel-name.ts

@@ -1,17 +1,16 @@
 import "server-only";
 
 import { env } from "@/env";
-import { FALLBACK_HOTEL_NAME } from "@/lib/brand";
 import { siteSettings } from "@/lib/services/site-settings";
 
 /**
- * Resolve the public hotel name: CMS setting → HOTEL_NAME env → FALLBACK_HOTEL_NAME.
+ * Resolve the public hotel name: CMS `hotel_name` setting, falling back to the
+ * required HOTEL_NAME env var. There is no hardcoded preset — the site must be
+ * configured, otherwise HOTEL_NAME fails validation at startup.
  */
 export async function resolveHotelName(): Promise<string> {
-	const fromSettings = await siteSettings.get("hotel_name", env.HOTEL_NAME);
-	const trimmed = fromSettings?.trim();
-	if (trimmed) return trimmed;
-	const fromEnv = env.HOTEL_NAME?.trim();
-	if (fromEnv) return fromEnv;
-	return FALLBACK_HOTEL_NAME;
+	const fromSettings = (
+		await siteSettings.get("hotel_name", env.HOTEL_NAME)
+	)?.trim();
+	return fromSettings || env.HOTEL_NAME;
 }