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/helpers/decimal-helpers.ts

@@ -1,8 +1,7 @@
 import * as z from 'zod';
 
-import type { Prisma } from '../../generated/prisma';
-
-import Decimal from "decimal.js";
+import { Prisma } from '../../generated/prisma';
+import Decimal from 'decimal.js';
 
 // DECIMAL HELPERS
 //------------------------------------------------------
@@ -24,7 +23,7 @@ export const isValidDecimalInput = (
   if (v === undefined || v === null) return false;
   return (
     // Explicit instance checks first
-    v instanceof Decimal ||
+    v instanceof Prisma.Decimal ||
     // If Decimal.js is present and imported by the generator, this symbol exists at runtime
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-ignore - Decimal may be undefined when not installed; codegen controls the import