terraform: add radarr/sonarr API keys for exportarr

Add vault secrets for Radarr and Sonarr API keys to enable
exportarr metrics collection on monitoring01.

- services/exportarr/radarr - Radarr API key
- services/exportarr/sonarr - Sonarr API key
- Grant monitoring01 access to services/exportarr/*

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

terraform/vault/variables.tf

@@ -80,3 +80,17 @@ variable "nixos_exporter_nkey" {
   sensitive   = true
 }
 
+variable "radarr_api_key" {
+  description = "Radarr API key for exportarr metrics"
+  type        = string
+  default     = "PLACEHOLDER"
+  sensitive   = true
+}
+
+variable "sonarr_api_key" {
+  description = "Sonarr API key for exportarr metrics"
+  type        = string
+  default     = "PLACEHOLDER"
+  sensitive   = true
+}
+