feat(ui): add /dash route, shared nav, project dashboard with /v1/projects API

Restructure routes: / and /dash show a project overview dashboard,
/activity hosts the existing timeline, /cv remains. Shared Layout
component provides consistent nav header and footer across all routes.

New /v1/projects endpoint aggregates per-repo activity stats (commits,
issues, PRs, date range) from existing event data via SQL. Dashboard
ranks projects by weighted recency + volume score and renders a card
grid.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/Layout.tsx

@@ -0,0 +1,42 @@
+import { NavLink, Outlet } from 'react-router-dom';
+import Container from 'react-bootstrap/Container';
+
+const externalLinks = [
+  { url: 'https://linkedin.com/in/thijssen/', label: 'linkedin' },
+  { url: 'https://stackoverflow.com/users/68115/grenade', label: 'stackoverflow' },
+  { url: 'https://github.com/grenade', label: 'github' },
+  { url: 'https://git.lair.cafe/grenade', label: 'gitea' },
+];
+
+export function Layout() {
+  return (
+    <>
+      <Container className="py-4">
+        <header className="site-header d-flex flex-wrap justify-content-between align-items-center mb-4">
+          <h1 className="mb-0">hi, i'm rob</h1>
+          <nav className="d-flex flex-wrap gap-3 align-items-center">
+            <NavLink to="/" end>dash</NavLink>
+            <NavLink to="/activity">activity</NavLink>
+            <NavLink to="/cv">cv</NavLink>
+            <span className="nav-divider">|</span>
+            {externalLinks.map((el) => (
+              <a
+                key={el.url}
+                href={el.url}
+                target="_blank"
+                rel="noopener noreferrer"
+              >
+                {el.label}
+              </a>
+            ))}
+          </nav>
+        </header>
+        <Outlet />
+      </Container>
+      <footer className="site-footer">
+        no cookies are set or read by this site, which is why no consent banner
+        is shown.
+      </footer>
+    </>
+  );
+}