Add site footer and switch display font to Sora, bump to 0.5.0

Adds a Footer component (credit line, repo/buttplug.io links) below main
content on all app pages, with the layout shell now flex-column so it
sticks to the bottom on short pages. Also swaps the display font from
Space Grotesk to Sora (after trying Fraunces, a serif, which didn't fit).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/(app)/layout.tsx

@@ -1,14 +1,16 @@
 import { NavBar } from "@/components/layout/NavBar";
 import { Breadcrumbs } from "@/components/layout/Breadcrumbs";
+import { Footer } from "@/components/layout/Footer";
 
 export default function AppLayout({ children }: { children: React.ReactNode }) {
   return (
-    <div className="min-h-dvh">
+    <div className="flex min-h-dvh flex-col">
       <NavBar />
-      <main className="mx-auto max-w-6xl px-4 py-8">
+      <main className="mx-auto w-full max-w-6xl flex-1 px-4 py-8">
         <Breadcrumbs />
         {children}
       </main>
+      <Footer />
     </div>
   );
 }