feat(whatsapp): add sendReadReceipts config option

Add option to disable automatic read receipts for WhatsApp messages.
When set to false, Clawdbot will not mark messages as read (blue ticks).

Closes #344

Changes:
- Add sendReadReceipts to WhatsAppConfig and WhatsAppAccountConfig types
- Add sendReadReceipts to zod schemas for validation
- Add sendReadReceipts to ResolvedWhatsAppAccount with fallback chain
- Pass sendReadReceipts through to monitorWebInbox
- Gate sock.readMessages() call based on config option

Default behavior (true) is preserved - only explicitly setting false
will disable read receipts.

src/web/auto-reply/monitor.ts

@@ -174,6 +174,7 @@ export async function monitorWebChannel(
       accountId: account.accountId,
       authDir: account.authDir,
       mediaMaxMb: account.mediaMaxMb,
+      sendReadReceipts: account.sendReadReceipts,
       onMessage: async (msg: WebInboundMsg) => {
         handledMessages += 1;
         lastMessageAt = Date.now();