feat(GRO-106): STOP/HELP compliance + consent log

- Add detectKeyword() and handleConsentKeyword() in consent.ts
- Wire keyword detection into handleMessageReceived() in inbound.ts
- Add 24-unit test suite for consent.ts covering all keywords,
  case insensitivity, whitespace tolerance, idempotency, and
  help keyword state preservation

Fixes from QA review:
- Use getDb() instead of non-existent db export; import Db type
- Destructure clientId from findOrCreateConversation result
- Rename staffId → sentByStaffId in sendMessage call
- Remove messagingHelpReply query (column not yet in schema)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/services/messaging/inbound.ts

@@ -1,5 +1,7 @@
 import { getDb, conversations, messages, businessSettings, clients, eq, and } from "@groombook/db";
 import { v4 as uuidv4 } from "uuid";
+import { detectKeyword, handleConsentKeyword } from "./consent.js";
+import { sendMessage } from "./outbound.js";
 
 export interface TelnyxMessageReceivedPayload {
   data: {
@@ -152,7 +154,7 @@ export async function handleMessageReceived(payload: TelnyxMessageReceivedPayloa
     throw new Error(`No business owns messaging number: ${toPhone}`);
   }
 
-  const { id: conversationId } = await findOrCreateConversation(businessId, fromPhone, toPhone);
+  const { id: conversationId, clientId } = await findOrCreateConversation(businessId, fromPhone, toPhone);
 
   await getDb()
     .update(conversations)
@@ -167,6 +169,22 @@ export async function handleMessageReceived(payload: TelnyxMessageReceivedPayloa
     "received"
   );
 
+  const keyword = detectKeyword(message.body ?? "");
+  if (keyword) {
+    const { replyText } = await handleConsentKeyword({
+      clientId,
+      businessId,
+      kind: keyword.kind,
+      db: getDb(),
+    });
+    await sendMessage({
+      businessId,
+      clientId,
+      body: replyText,
+      sentByStaffId: undefined,
+    });
+  }
+
   return { conversationId, messageId };
 }