feat(app): add seggwat feedback widget and update README

Add feedback widget script with right-side button position and
screenshot support. Remove rating widget from sidebar footer.
Redesign README with centered logo, badges, and structured layout.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app.rs

@@ -64,6 +64,16 @@ const GOOGLE_FONTS: &str = "https://fonts.googleapis.com/css2?\
 #[component]
 pub fn App() -> Element {
     rsx! {
+        // Seggwat feedback widget
+        document::Script {
+            src: "https://seggwat.com/static/widgets/v1/seggwat-feedback.js",
+            r#defer: true,
+            "data-project-key": "a04b8cf1-9177-42ce-8a7b-084f38b99799",
+            "data-button-color": "#6d85c6",
+            "data-button-position": "right-side",
+            "data-enable-screenshots": "true",
+        }
+
         document::Link { rel: "icon", href: FAVICON }
         document::Link { rel: "manifest", href: MANIFEST }
         document::Meta { name: "theme-color", content: "#4B3FE0" }