docs: document queue processing best practices

[pepperfm]

Summary

• document synchronous sending and outbound queue selection
• recommend fixed queues, dedicated worker pools, and optional Horizon supervisors
• document Telegram rate limits, current 429 behavior, and application-owned throttling
• add guidance for background webhook jobs, authorization, idempotency, and ordering

Closes #563

Testing

• vendor/bin/pest tests/Unit/Concerns/HasBotsAndChatsTest.php tests/Feature/DocumentationCodeSnippetsTest.php
• PHP syntax validation for complete documentation examples
• relative documentation link checks
• git diff --cached --check