[infra] Add Cloudflare provider to all stack lock files and generated providers

Terragrunt now generates cloudflare_provider.tf (Vault-sourced API key)
and includes cloudflare in required_providers. These are the generated
files from running `terragrunt init -upgrade` across all stacks.

[ci skip]

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

stacks/webhook_handler/providers.tf

@@ -5,6 +5,10 @@ terraform {
       source  = "hashicorp/vault"
       version = "~> 4.0"
     }
+    cloudflare = {
+      source  = "cloudflare/cloudflare"
+      version = "~> 4"
+    }
   }
 }