feat(ui): add auth pages, company rail, inbox redesign, and page improvements

Add Auth sign-in/sign-up page and InviteLanding page for invite acceptance.
Add CloudAccessGate that checks deployment mode and redirects to /auth when
session is required. Add CompanyRail with drag-and-drop company switching.
Add MarkdownBody prose renderer. Redesign Inbox with category filters and
inline join-request approval. Refactor AgentDetail to overview/configure/runs
views with claude-login support. Replace navigate() anti-patterns with <Link>
components in Dashboard and MetricCard. Add live-run indicators in sidebar
agents. Fix LiveUpdatesProvider cache key resolution for issue identifiers.
Add auth, health, and access API clients.

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

ui/src/pages/ApprovalDetail.tsx

@@ -13,6 +13,7 @@ import { Button } from "@/components/ui/button";
 import { Textarea } from "@/components/ui/textarea";
 import { CheckCircle2, ChevronRight, Sparkles } from "lucide-react";
 import type { ApprovalComment } from "@paperclip/shared";
+import { MarkdownBody } from "../components/MarkdownBody";
 
 export function ApprovalDetail() {
   const { approvalId } = useParams<{ approvalId: string }>();
@@ -329,7 +330,7 @@ export function ApprovalDetail() {
                   {new Date(comment.createdAt).toLocaleString()}
                 </span>
               </div>
-              <p className="text-sm whitespace-pre-wrap">{comment.body}</p>
+              <MarkdownBody className="text-sm">{comment.body}</MarkdownBody>
             </div>
           ))}
         </div>