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/Auth.tsx

@@ -0,0 +1,141 @@
+import { useEffect, useMemo, useState } from "react";
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import { useNavigate, useSearchParams } from "react-router-dom";
+import { authApi } from "../api/auth";
+import { queryKeys } from "../lib/queryKeys";
+import { Button } from "@/components/ui/button";
+
+type AuthMode = "sign_in" | "sign_up";
+
+export function AuthPage() {
+  const queryClient = useQueryClient();
+  const navigate = useNavigate();
+  const [searchParams] = useSearchParams();
+  const [mode, setMode] = useState<AuthMode>("sign_in");
+  const [name, setName] = useState("");
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [error, setError] = useState<string | null>(null);
+
+  const nextPath = useMemo(() => searchParams.get("next") || "/", [searchParams]);
+  const { data: session, isLoading: isSessionLoading } = useQuery({
+    queryKey: queryKeys.auth.session,
+    queryFn: () => authApi.getSession(),
+    retry: false,
+  });
+
+  useEffect(() => {
+    if (session) {
+      navigate(nextPath, { replace: true });
+    }
+  }, [session, navigate, nextPath]);
+
+  const mutation = useMutation({
+    mutationFn: async () => {
+      if (mode === "sign_in") {
+        await authApi.signInEmail({ email: email.trim(), password });
+        return;
+      }
+      await authApi.signUpEmail({
+        name: name.trim(),
+        email: email.trim(),
+        password,
+      });
+    },
+    onSuccess: async () => {
+      setError(null);
+      await queryClient.invalidateQueries({ queryKey: queryKeys.auth.session });
+      await queryClient.invalidateQueries({ queryKey: queryKeys.companies.all });
+      navigate(nextPath, { replace: true });
+    },
+    onError: (err) => {
+      setError(err instanceof Error ? err.message : "Authentication failed");
+    },
+  });
+
+  const canSubmit =
+    email.trim().length > 0 &&
+    password.trim().length >= 8 &&
+    (mode === "sign_in" || name.trim().length > 0);
+
+  if (isSessionLoading) {
+    return <div className="mx-auto max-w-md py-16 text-sm text-muted-foreground">Loading...</div>;
+  }
+
+  return (
+    <div className="mx-auto max-w-md py-10">
+      <div className="rounded-lg border border-border bg-card p-6 shadow-sm">
+        <h1 className="text-xl font-semibold">
+          {mode === "sign_in" ? "Sign in to Paperclip" : "Create your Paperclip account"}
+        </h1>
+        <p className="mt-1 text-sm text-muted-foreground">
+          {mode === "sign_in"
+            ? "Use your email and password to access this instance."
+            : "Create an account for this instance. Email confirmation is not required in v1."}
+        </p>
+
+        <form
+          className="mt-5 space-y-3"
+          onSubmit={(event) => {
+            event.preventDefault();
+            mutation.mutate();
+          }}
+        >
+          {mode === "sign_up" && (
+            <label className="block text-sm">
+              <span className="mb-1 block text-muted-foreground">Name</span>
+              <input
+                className="w-full rounded-md border border-border bg-background px-3 py-2 text-sm"
+                value={name}
+                onChange={(event) => setName(event.target.value)}
+                autoComplete="name"
+              />
+            </label>
+          )}
+          <label className="block text-sm">
+            <span className="mb-1 block text-muted-foreground">Email</span>
+            <input
+              className="w-full rounded-md border border-border bg-background px-3 py-2 text-sm"
+              type="email"
+              value={email}
+              onChange={(event) => setEmail(event.target.value)}
+              autoComplete="email"
+            />
+          </label>
+          <label className="block text-sm">
+            <span className="mb-1 block text-muted-foreground">Password</span>
+            <input
+              className="w-full rounded-md border border-border bg-background px-3 py-2 text-sm"
+              type="password"
+              value={password}
+              onChange={(event) => setPassword(event.target.value)}
+              autoComplete={mode === "sign_in" ? "current-password" : "new-password"}
+            />
+          </label>
+          {error && <p className="text-sm text-destructive">{error}</p>}
+          <Button type="submit" disabled={!canSubmit || mutation.isPending} className="w-full">
+            {mutation.isPending
+              ? "Working..."
+              : mode === "sign_in"
+                ? "Sign In"
+                : "Create Account"}
+          </Button>
+        </form>
+
+        <div className="mt-4 text-sm text-muted-foreground">
+          {mode === "sign_in" ? "Need an account?" : "Already have an account?"}{" "}
+          <button
+            type="button"
+            className="font-medium text-foreground underline underline-offset-2"
+            onClick={() => {
+              setError(null);
+              setMode(mode === "sign_in" ? "sign_up" : "sign_in");
+            }}
+          >
+            {mode === "sign_in" ? "Create one" : "Sign in"}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}