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/variants/input/TelnyxSettings.input.ts

@@ -0,0 +1,16 @@
+import * as z from 'zod';
+// prettier-ignore
+export const TelnyxSettingsInputSchema = z.object({
+    id: z.number().int(),
+    userId: z.number().int(),
+    apiKey: z.string(),
+    accountSid: z.string().optional().nullable(),
+    phoneNumber: z.string(),
+    texmlApplicationId: z.string().optional().nullable(),
+    messagingProfileId: z.string().optional().nullable(),
+    webhookPublicKey: z.string().optional().nullable(),
+    greetingMessage: z.string().optional().nullable(),
+    user: z.unknown()
+}).strict();
+
+export type TelnyxSettingsInputType = z.infer<typeof TelnyxSettingsInputSchema>;