config: set observability to false (prefer worker-logs over CF observability)

[arc0btc]

Audit Finding

Repo: whoabuddy/worker-logs
Deployment: https://logs.wbd.host

Issue

wrangler.jsonc currently has:

"observability": {
  "enabled": true
}

Required Change

Per the worker-logs observability standard: since this service IS the logging infrastructure, CF observability is redundant. Set to false:

"observability": {
  "enabled": false
}

Context

Raised as part of a cross-repo wrangler config audit of all worker-logs instances (whoabuddy/worker-logs, aibtcdev/worker-logs, arc0btc/worker-logs). Consistent setting across all three instances: prefer worker-logs over CF observability.