feat: AI chat system with LangGraph, multi-step patient flows, and appointment rescheduling

- Add floating chat window Hand-off to AI toggle (per-patient) and after-hours AI toggle (global)
- Add LangGraph-powered appointment reminder flow: AI introduces itself, classifies YES/NO, handles confirmation with appointment date/time
- Add multi-step rescheduling flow: ASAP vs next week, tomorrow offer, Mon/Tue/Wed picker, morning/afternoon time slot — automatically updates appointment in DB
- Add new patient / after-hours flow: new vs existing patient, dental insurance check, MassHealth Selenium eligibility check (auto-uses saved member ID + DOB for existing patients), self-pay fallback
- Add AI Chat Settings page (Settings → Advanced) with editable greeting templates and LangGraph flow diagrams for both reminder and new-patient flows
- Add Schedule a New Patient template option in chat window, starts new-patient conversation flow
- Add GET/PUT endpoints for AI handoff, after-hours handoff, and AI chat templates
- Add multilingual support (7 languages) across all AI reply nodes with LLM generation and hardcoded fallbacks
- Add pending reschedule in-memory store and conversation stage tracking across all flows

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

apps/Frontend/src/pages/patient-connection-page.tsx

@@ -13,6 +13,7 @@ import {
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { Badge } from "@/components/ui/badge";
+import { Switch } from "@/components/ui/switch";
 import {
   Phone,
   PhoneCall,
@@ -22,6 +23,7 @@ import {
   MessageSquare,
   Send,
   X,
+  MoonStar,
 } from "lucide-react";
 import { SmsTemplateDialog } from "@/components/patient-connection/sms-template-diaog";
 import { MessageThread } from "@/components/patient-connection/message-thread";
@@ -35,8 +37,36 @@ export default function PatientConnectionPage() {
   const [selectedPatient, setSelectedPatient] = useState<Patient | null>(null);
   const [isSmsDialogOpen, setIsSmsDialogOpen] = useState(false);
   const [showMessaging, setShowMessaging] = useState(false);
+  const [afterHoursEnabled, setAfterHoursEnabled] = useState(true);
   const { toast } = useToast();
 
+  useQuery<{ enabled: boolean }>({
+    queryKey: ["/api/twilio/after-hours-handoff"],
+    queryFn: async () => {
+      const res = await apiRequest("GET", "/api/twilio/after-hours-handoff");
+      return res.json();
+    },
+    onSuccess: (data: { enabled: boolean }) => setAfterHoursEnabled(data.enabled),
+  } as any);
+
+  const afterHoursMutation = useMutation({
+    mutationFn: async (enabled: boolean) =>
+      apiRequest("PUT", "/api/twilio/after-hours-handoff", { enabled }),
+    onSuccess: (_: any, enabled: boolean) => {
+      toast({
+        title: enabled ? "After-hours AI enabled" : "After-hours AI disabled",
+        description: enabled
+          ? "AI will automatically handle messages outside office hours."
+          : "After-hours messages will not receive an automatic AI reply.",
+      });
+    },
+  });
+
+  const handleAfterHoursToggle = (enabled: boolean) => {
+    setAfterHoursEnabled(enabled);
+    afterHoursMutation.mutate(enabled);
+  };
+
   const toggleMobileMenu = () => {
     setIsMobileMenuOpen(!isMobileMenuOpen);
   };
@@ -175,6 +205,16 @@ export default function PatientConnectionPage() {
               Search and communicate with patients
             </p>
           </div>
+
+          {/* After-hours AI toggle */}
+          <div className="flex items-center gap-2 px-4 py-2 rounded-lg border bg-white shadow-sm">
+            <MoonStar className={`h-4 w-4 ${afterHoursEnabled ? "text-primary" : "text-muted-foreground"}`} />
+            <span className="text-sm font-medium">Hand off to AI after hours</span>
+            <Switch
+              checked={afterHoursEnabled}
+              onCheckedChange={handleAfterHoursToggle}
+            />
+          </div>
         </div>
       </div>
 

apps/Frontend/src/pages/settings-page.tsx

@@ -19,6 +19,7 @@ import { OfficeHoursCard } from "@/components/settings/office-hours-card";
 import { OfficeContactCard } from "@/components/settings/office-contact-card";
 import { ProcedureTimeslotCard } from "@/components/settings/procedure-timeslot-card";
 import { InsuranceContactCard } from "@/components/settings/insurance-contact-card";
+import { AiChatSettingsCard } from "@/components/settings/ai-chat-settings-card";
 
 type SectionId =
   | "staff"
@@ -29,6 +30,7 @@ type SectionId =
   | "programs"
   | "twilio"
   | "ai"
+  | "aichat"
   | "officehours"
   | "officecontact"
   | "proceduretimeslot"
@@ -259,6 +261,9 @@ export default function SettingsPage() {
       case "ai":
         return <AiSettingsCard />;
 
+      case "aichat":
+        return <AiChatSettingsCard />;
+
       case "officehours":
         return <OfficeHoursCard />;