feat(web): add staff sign-in entrance (judge / instructor) to landing

The landing page only routed attendees; /judge and /admin were
unlinked. Add a subtle "Staff sign-in ▾" disclosure in the header
linking to the judge and instructor consoles (both already gated by
AccessGate). Attendee hero is unchanged.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

src/pages/Landing.test.tsx

@@ -33,6 +33,12 @@ describe('Landing', () => {
     ctas.forEach((cta) => expect(cta).toHaveAttribute('href', '/workshop'))
   })
 
+  it('exposes staff sign-in entrances for judge and instructor', () => {
+    renderLanding()
+    expect(screen.getByRole('link', { name: /judge/i })).toHaveAttribute('href', '/judge')
+    expect(screen.getByRole('link', { name: /instructor/i })).toHaveAttribute('href', '/admin')
+  })
+
   it('lists the programme timeline with at least 5 phases', () => {
     renderLanding()
     const programme = screen.getByTestId('programme')

src/pages/Landing.tsx

@@ -44,6 +44,25 @@ export function Landing() {
           <Link to="/lecture" className="font-mono text-[11px] text-muted-foreground hover:text-foreground tracking-widest uppercase">
             Lecture
           </Link>
+          <details className="relative group [&_summary::-webkit-details-marker]:hidden">
+            <summary className="list-none cursor-pointer select-none font-mono text-[11px] text-muted-foreground hover:text-foreground tracking-widest uppercase">
+              Staff sign-in ▾
+            </summary>
+            <div className="absolute right-0 mt-2 w-40 rounded-md border border-border bg-background shadow-md py-1 z-50">
+              <Link
+                to="/judge"
+                className="block px-3 py-2 font-mono text-[11px] text-muted-foreground hover:text-foreground hover:bg-secondary/60 tracking-widest uppercase"
+              >
+                Judge
+              </Link>
+              <Link
+                to="/admin"
+                className="block px-3 py-2 font-mono text-[11px] text-muted-foreground hover:text-foreground hover:bg-secondary/60 tracking-widest uppercase"
+              >
+                Instructor
+              </Link>
+            </div>
+          </details>
           <Button asChild size="sm">
             <Link to="/workshop">Enter workshop →</Link>
           </Button>