feat: Add 15 backend service stub files with TODO implementations

Stub files for all services declared in services/mod.rs:
- Panel adapters: AMP, Pterodactyl, Companion (NATS-based)
- Wipe pipeline: WipeEngine, Scheduler, HealthChecker, BackupManager
- Infrastructure: NatsBridge (JetStream), SteamUpdateWatcher, MapManager
- Notifications: Discord webhooks, Pushbullet push notifications
- Platform: LicenseService, CloudflareService, encryption utilities

Each file has struct definitions, method signatures with proper types,
and descriptive TODO comments outlining the implementation plan.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/services/cloudflare.rs

@@ -0,0 +1,46 @@
+use anyhow::Result;
+
+/// Cloudflare DNS management service.
+///
+/// Manages DNS records for tenant subdomains (e.g., myserver.corrosion.gg)
+/// and custom domains. Uses the Cloudflare API v4 to create and manage
+/// CNAME records pointing to the platform's load balancer.
+pub struct CloudflareService {
+    // TODO: Add fields:
+    // - api_token: String
+    // - zone_id: String (Cloudflare zone for the base domain)
+    // - base_domain: String (e.g., "corrosion.gg")
+}
+
+impl CloudflareService {
+    /// Create a subdomain CNAME record for a new license.
+    ///
+    /// Creates: {subdomain}.{base_domain} -> platform LB
+    pub async fn create_subdomain(&self, _subdomain: &str) -> Result<String> {
+        // TODO: POST /zones/{zone_id}/dns_records
+        // TODO: Type: CNAME, Name: {subdomain}, Content: platform target
+        // TODO: Proxied: true (orange cloud)
+        // TODO: Return the DNS record ID for later management
+        todo!()
+    }
+
+    /// Delete a subdomain CNAME record.
+    ///
+    /// Called when a license is deactivated or transferred.
+    pub async fn delete_subdomain(&self, _dns_record_id: &str) -> Result<()> {
+        // TODO: DELETE /zones/{zone_id}/dns_records/{dns_record_id}
+        todo!()
+    }
+
+    /// Add a custom domain with CNAME verification.
+    ///
+    /// Returns the CNAME target that the customer needs to configure
+    /// on their own DNS provider.
+    pub async fn add_custom_domain(&self, _custom_domain: &str) -> Result<String> {
+        // TODO: Generate verification CNAME target
+        // TODO: Create verification DNS record in Cloudflare
+        // TODO: Optionally configure SSL for custom hostname via Cloudflare
+        // TODO: Return the CNAME target for customer DNS setup
+        todo!()
+    }
+}