fix(portal): redirect unauthenticated users to login — never show portal chrome (GRO-309)

- CustomerPortal.tsx: add initComplete state to track async session
  initialization. After init completes with no valid session, redirect:
  staff dev users → /admin, all others → /login
- Dashboard.tsx: change !sessionId fallback from dead-end UI to
  <Navigate to="/login" replace /> (defense-in-depth)
- All 85 web unit tests pass

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/web/src/portal/CustomerPortal.tsx

@@ -1,5 +1,5 @@
 import { useState, useCallback, useEffect, useRef } from "react";
-import { useSearchParams } from "react-router-dom";
+import { useSearchParams, Navigate } from "react-router-dom";
 import {
   Home, Calendar, PawPrint, FileText, CreditCard, MessageSquare,
   Settings, LogOut, Shield,
@@ -38,6 +38,7 @@ export function CustomerPortal() {
   const [session, setSession] = useState<ImpersonationSession | null>(null);
   const [sessionExtended, setSessionExtended] = useState(false);
   const [clientName, setClientName] = useState<string>("");
+  const [initComplete, setInitComplete] = useState(false);
   const { branding } = useBranding();
   const [searchParams, setSearchParams] = useSearchParams();
 
@@ -68,7 +69,8 @@ export function CustomerPortal() {
         })
         .catch(() => {
           setSearchParams({}, { replace: true });
-        });
+        })
+        .finally(() => setInitComplete(true));
       return;
     }
 
@@ -90,7 +92,11 @@ export function CustomerPortal() {
             setClientName(devUser.name);
           }
         })
-        .catch(() => {});
+        .catch(() => {})
+        .finally(() => setInitComplete(true));
+    } else {
+      // No valid session: staff dev users and unauthenticated users fall through here
+      setInitComplete(true);
     }
   }, []);
 
@@ -168,6 +174,16 @@ export function CustomerPortal() {
 
   const avatarInitials = (clientName.split(" ")[0] || "G").charAt(0).toUpperCase();
 
+  // After init completes, redirect unauthenticated users to /login and staff to /admin
+  // The portal chrome must NEVER be visible to users without a valid client session
+  if (initComplete && !session) {
+    const devUser = getDevUser();
+    if (devUser && devUser.type === "staff") {
+      return <Navigate to="/admin" replace />;
+    }
+    return <Navigate to="/login" replace />;
+  }
+
   return (
     <div
       className="min-h-screen bg-[#faf8f5] font-sans"