feat: domain-based branding (humorunits.com / dickloads.com)

- src/lib/brand.ts: Brand config map, getBrand() reads hostname server-side
- src/routes/+layout.server.ts: new, passes brand to layout
- +layout.svelte: site name and footer driven by brand config
- humorunits.com footer: 'invented conversions for ridiculous people'
- dickloads.com footer: placeholder (pending Shannon's pick)

src/lib/brand.ts

@@ -0,0 +1,32 @@
+/**
+ * Brand configuration keyed by hostname (www-stripped).
+ * Add new domains here — no other changes needed.
+ */
+export interface Brand {
+  /** Site name shown in nav and page titles. */
+  name: string;
+  /** Footer tagline. */
+  footer: string;
+}
+
+const BRANDS: Record<string, Brand> = {
+  'humorunits.com': {
+    name: 'Humor Units',
+    footer: 'Humor Units — invented conversions for ridiculous people.',
+  },
+  'dickloads.com': {
+    name: 'Dick Loads',
+    footer: 'Dick Loads — serious units for serious people.',
+  },
+};
+
+const DEFAULT_BRAND = BRANDS['humorunits.com'];
+
+export function getBrand(requestUrl: string): Brand {
+  try {
+    const host = new URL(requestUrl).hostname.replace(/^www\./, '');
+    return BRANDS[host] ?? DEFAULT_BRAND;
+  } catch {
+    return DEFAULT_BRAND;
+  }
+}