fix(GRO-1003): address CI typecheck and lint failures on PR #379

Typecheck fixes:
- telnyx.ts:48 — coerce undefined to null for signature param
- inbound.ts/outbound.ts — add null guards on .returning() results
- schema.ts — add updatedAt to messages table
- package.json — add uuid and @types/uuid

Lint fixes:
- telnyx.ts — remove unused resolveBusinessIdByMessagingNumber import
- inbound.ts — remove unused messageDirectionEnum, messageStatusEnum imports
- inbound.ts — remove unused buildFindOrCreateConversationParams function
- inbound.test.ts — remove unused resolveBusinessIdByMessagingNumber import
- outbound.test.ts — remove unused mockEq/mockAnd variables
- outbound.test.ts — fix vi.mock path for sms.js (../../sms.js)

apps/api/package.json

@@ -24,6 +24,7 @@
     "nodemailer": "^6.9.16",
     "stripe": "^22.0.0",
     "telnyx": "^1.23.0",
+    "uuid": "^11.0.5",
 
     "zod": "^4.3.6"
   },
@@ -31,6 +32,7 @@
     "@types/node": "^22.10.7",
     "@types/node-cron": "^3.0.11",
     "@types/nodemailer": "^6.4.17",
+    "@types/uuid": "^10.0.0",
     "@vitest/coverage-v8": "^3.2.4",
     "eslint": "^9.18.0",
     "tsx": "^4.19.2",