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/Projects.tsx

@@ -1,5 +1,4 @@
 import { useEffect } from "react";
-import { useNavigate } from "react-router-dom";
 import { useQuery } from "@tanstack/react-query";
 import { projectsApi } from "../api/projects";
 import { useCompany } from "../context/CompanyContext";
@@ -17,7 +16,6 @@ export function Projects() {
   const { selectedCompanyId } = useCompany();
   const { openNewProject } = useDialog();
   const { setBreadcrumbs } = useBreadcrumbs();
-  const navigate = useNavigate();
 
   useEffect(() => {
     setBreadcrumbs([{ label: "Projects" }]);
@@ -36,7 +34,7 @@ export function Projects() {
   return (
     <div className="space-y-4">
       <div className="flex items-center justify-end">
-        <Button size="sm" onClick={openNewProject}>
+        <Button size="sm" variant="outline" onClick={openNewProject}>
           <Plus className="h-4 w-4 mr-1" />
           Add Project
         </Button>
@@ -61,7 +59,7 @@ export function Projects() {
               key={project.id}
               title={project.name}
               subtitle={project.description ?? undefined}
-              onClick={() => navigate(`/projects/${project.id}`)}
+              to={`/projects/${project.id}`}
               trailing={
                 <div className="flex items-center gap-3">
                   {project.targetDate && (