Add Continue with Google button to register page

- Add Google OAuth button matching login page style
- Add divider with 'or' text between form and OAuth button
- Button calls signIn('google') with redirect to /app
- Matches task 11.3 requirements

src/app/(public)/register/page.tsx

@@ -128,6 +128,26 @@ export default function RegisterPage() {
               </Button>
             </form>
 
+            <div className="relative my-4">
+              <div className="absolute inset-0 flex items-center">
+                <span className="w-full border-t border-border" />
+              </div>
+              <div className="relative flex justify-center text-xs uppercase">
+                <span className="bg-card px-2 text-muted-foreground font-mono">
+                  or
+                </span>
+              </div>
+            </div>
+
+            <Button
+              type="button"
+              variant="outline"
+              className="w-full font-mono text-sm"
+              onClick={() => signIn("google", { redirectTo: "/app" })}
+            >
+              Continue with Google
+            </Button>
+
             <p className="text-center text-xs text-muted-foreground mt-4">
               Already have an account?{" "}
               <Link