feat(ui): add public landing page with impressum and privacy pages

Introduce a marketing landing page at `/` with hero section, feature grid,
how-it-works steps, CTA banner, and footer. Move the authenticated dashboard
to `/dashboard`. Add static Impressum and Privacy Policy pages for EU legal
compliance. Update login redirect defaults accordingly.

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

src/app.rs

@@ -3,14 +3,20 @@ use dioxus::prelude::*;
 
 /// Application routes.
 ///
-/// `OverviewPage` is wrapped in the `AppShell` layout so the sidebar
-/// renders around every authenticated page. The `/login` route remains
-/// outside the shell (unauthenticated).
+/// Public pages (`LandingPage`, `ImpressumPage`, `PrivacyPage`) live
+/// outside the `AppShell` layout. Authenticated pages like `OverviewPage`
+/// are wrapped in `AppShell` which renders the sidebar.
 #[derive(Debug, Clone, Routable, PartialEq)]
 #[rustfmt::skip]
 pub enum Route {
+    #[route("/")]
+    LandingPage {},
+    #[route("/impressum")]
+    ImpressumPage {},
+    #[route("/privacy")]
+    PrivacyPage {},
     #[layout(AppShell)]
-        #[route("/")]
+        #[route("/dashboard")]
         OverviewPage {},
     #[end_layout]
     #[route("/login?:redirect_url")]