Frontend redesign chunk 4: navigation and routing

Rewrite Nav.tsx to the five-destination IA from UI_REDESIGN.md §3 (Live,
Incidents, Archive, Watch, Network) on tokens/sans type, with Settings,
Admin, Trips and Profile moved into the avatar dropdown instead of sitting
as nav peers. Network stays gated to admin/operator, matching the write
boundary its constituent pages (nodes/systems/tokens) already had.

Delete app/dashboard/page.tsx — its incident cards become the Live rail,
its node cards become Network, its call table becomes Archive; nothing on
it is unique. Add app/map/page.tsx -> redirect('/') and rewrite
app/calls/page.tsx -> redirect('/incidents') (Archive/search is blocked on
backend work, chunk 12).

ChromeSwitcher now gives a signed-in user at "/" the app shell instead of
marketing chrome; app/page.tsx branches the same way, sending a signed-in
provisioned user to /incidents as an honest interim until the Live screen
itself lands (chunk 6) — marketing content and behavior for signed-out
visitors is unchanged.

Left the light-mode !important overrides in globals.css in place past this
chunk (deviating from the chunk 4 acceptance criteria) — they still back
every page outside this redesign's 11-chunk scope (settings, admin,
profile, marketing). Deleting them now would break light mode on all of
those. Logged in DEFERRED.md.

Per UI_REDESIGN.md chunk 4.

drb-frontend/components/ChromeSwitcher.tsx

@@ -45,7 +45,13 @@ export function ChromeSwitcher({ children }: { children: React.ReactNode }) {
     router.replace("/onboarding");
   }, [loading, user, orgId, pathname, router]);
 
-  if (MARKETING_PATHS.has(pathname)) {
+  // "/" is marketing for a signed-out visitor, but the moment someone is
+  // signed in it's Live — the map is the home screen (UI_REDESIGN.md §3),
+  // not a marketing page. Every other marketing path stays marketing
+  // regardless of auth state.
+  const showMarketingChrome = MARKETING_PATHS.has(pathname) && !(pathname === "/" && user);
+
+  if (showMarketingChrome) {
     return (
       <>
         <MarketingHeader />
@@ -55,6 +61,17 @@ export function ChromeSwitcher({ children }: { children: React.ReactNode }) {
     );
   }
 
+  // Live ("/") is full-bleed under its own top bar, not the padded
+  // max-width container the rest of the app uses.
+  if (pathname === "/" && user) {
+    return (
+      <>
+        <Nav />
+        <main className="h-[calc(100vh-3.75rem)]">{children}</main>
+      </>
+    );
+  }
+
   return (
     <>
       <Nav />