feat: migrate SMS/voice to Telnyx (TeXML), keep browser dial pad on Twilio

Twilio now handles only the in-browser dial pad (Access Token + browser-Device
outbound TwiML); Telnyx takes over SMS, inbound voicemail, the AI voice
conversation loop, and staff-triggered outbound calls via TeXML. Adds
TelnyxSettings model, Communication.provider discriminator, new comms/routes
modules, and a real Telnyx Settings page.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/Frontend/src/components/patient-connection/message-thread.tsx

@@ -269,9 +269,9 @@ export function MessageThread({ patient, onBack, appointmentInfo }: MessageThrea
   const [pendingStartFlow, setPendingStartFlow] = useState<"new_patient" | "reschedule" | null>(null);
 
   useQuery<{ enabled: boolean }>({
-    queryKey: ["/api/twilio/ai-handoff", patient.id],
+    queryKey: ["/api/telnyx/ai-handoff", patient.id],
     queryFn: async () => {
-      const res = await apiRequest("GET", `/api/twilio/ai-handoff/${patient.id}`);
+      const res = await apiRequest("GET", `/api/telnyx/ai-handoff/${patient.id}`);
       return res.json();
     },
     onSuccess: (data: { enabled: boolean }) => setHandOffToAI(data.enabled),
@@ -289,7 +289,7 @@ export function MessageThread({ patient, onBack, appointmentInfo }: MessageThrea
 
   const handoffMutation = useMutation({
     mutationFn: async (enabled: boolean) =>
-      apiRequest("PUT", `/api/twilio/ai-handoff/${patient.id}`, { enabled }),
+      apiRequest("PUT", `/api/telnyx/ai-handoff/${patient.id}`, { enabled }),
   });
 
   const handleHandoffToggle = (enabled: boolean) => {
@@ -318,7 +318,7 @@ export function MessageThread({ patient, onBack, appointmentInfo }: MessageThrea
 
   const sendMessageMutation = useMutation({
     mutationFn: async (message: string) =>
-      apiRequest("POST", "/api/twilio/send-sms", {
+      apiRequest("POST", "/api/telnyx/send-sms", {
         to: patient.phone,
         message,
         patientId: patient.id,