chore: Update PR template with AI usage warning (#6951)

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: louislam

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,3 +1,10 @@
+<!--
+⚠️ NO AI SLOP!!!
+⚠️ If you just feed the issue to a code agent, generate code + LLM description, then ping for review without checking anything
+⚠️ You will be BANNED immediately
+Read more: https://github.com/louislam/uptime-kuma/issues/6260#issuecomment-3796504136
+-->
+
 # Summary
 
 In this pull request, the following changes are made: