rename: replace all user-facing 'Atlas' references with 'Vibn'

Updated UI text in: project-shell (tab label), AtlasChat (sender name),
FreshIdeaMain, TypeSelector, MigrateSetup, ChatImportSetup, FreshIdeaSetup,
CodeImportSetup, prd/page, build/page, projects/page, deployment/page,
activity/page, layout (page title/description), atlas-chat API route.
Code identifiers (AtlasChat component name, file names) unchanged.

Made-with: Cursor

app/layout.tsx

@@ -24,8 +24,8 @@ const ibmPlexMono = IBM_Plex_Mono({
 });
 
 export const metadata: Metadata = {
-  title: "VIBN — Build with Atlas",
-  description: "Chat with Atlas to define your product, then let AI build it.",
+  title: "VIBN — Build with Vibn",
+  description: "Chat with Vibn to define your product, then let AI build it.",
   manifest: "/manifest.json",
   appleWebApp: {
     capable: true,