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/User.input.ts

@@ -26,6 +26,7 @@ export const UserInputSchema = z.object({
     cloudFiles: z.array(z.unknown()),
     communications: z.array(z.unknown()),
     twilioSettings: z.unknown().optional().nullable(),
+    telnyxSettings: z.unknown().optional().nullable(),
     aiSettings: z.unknown().optional().nullable(),
     officeHours: z.unknown().optional().nullable(),
     officeContact: z.unknown().optional().nullable(),