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>

packages/db/shared/schemas/results/TelnyxSettingsCreateResult.schema.ts

@@ -0,0 +1,13 @@
+import * as z from 'zod';
+export const TelnyxSettingsCreateResultSchema = z.object({
+  id: z.number().int(),
+  userId: z.number().int(),
+  apiKey: z.string(),
+  accountSid: z.string().optional(),
+  phoneNumber: z.string(),
+  texmlApplicationId: z.string().optional(),
+  messagingProfileId: z.string().optional(),
+  webhookPublicKey: z.string().optional(),
+  greetingMessage: z.string().optional(),
+  user: z.unknown()
+});