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/backup_manager.rs

@@ -0,0 +1,78 @@
+use anyhow::Result;
+use chrono::{DateTime, Utc};
+use serde::Serialize;
+use uuid::Uuid;
+
+/// Metadata for a stored backup.
+#[derive(Debug, Clone, Serialize)]
+pub struct BackupInfo {
+    pub id: Uuid,
+    pub license_id: Uuid,
+    pub wipe_history_id: Option<Uuid>,
+    pub storage_path: String,
+    pub size_bytes: i64,
+    pub created_at: DateTime<Utc>,
+}
+
+/// Pre-wipe backup and rollback management.
+///
+/// Creates snapshots of server state (map, save data, plugin data,
+/// config files) before a wipe executes. Backups are used by the
+/// wipe engine's rollback mechanism if post-wipe verification fails.
+pub struct BackupManager {
+    // TODO: Add fields:
+    // - db: sqlx::PgPool
+    // - storage_base_path: String
+}
+
+impl BackupManager {
+    /// Create a pre-wipe backup of the server's current state.
+    ///
+    /// Captures: map/save files, plugin data directories, server.cfg,
+    /// and any other files configured for backup in the wipe profile.
+    /// Returns a backup reference ID stored in wipe_history.
+    pub async fn create_backup(
+        &self,
+        _license_id: Uuid,
+        _wipe_history_id: Uuid,
+    ) -> Result<String> {
+        // TODO: Resolve PanelAdapter for the server
+        // TODO: Download save files (map, sav, player data) via adapter
+        // TODO: Download plugin data directories via adapter
+        // TODO: Download server.cfg via adapter
+        // TODO: Bundle into archive (tar.gz)
+        // TODO: Write archive to backup storage
+        // TODO: Insert backup record in DB
+        // TODO: Return backup reference string
+        todo!()
+    }
+
+    /// Restore a previously created backup to the server.
+    ///
+    /// Used during rollback when post-wipe verification fails.
+    pub async fn restore_backup(&self, _backup_reference: &str) -> Result<()> {
+        // TODO: Load backup record from DB by reference
+        // TODO: Read backup archive from storage
+        // TODO: Extract archive contents
+        // TODO: Upload files back to server via PanelAdapter
+        // TODO: Log restoration details
+        todo!()
+    }
+
+    /// List all backups for a license, ordered by creation date (newest first).
+    pub async fn list_backups(&self, _license_id: Uuid) -> Result<Vec<BackupInfo>> {
+        // TODO: Query backup records from DB for this license
+        // TODO: Return sorted list
+        todo!()
+    }
+
+    /// Clean up old backups beyond the configured retention period/count.
+    pub async fn cleanup_old_backups(&self, _license_id: Uuid) -> Result<u32> {
+        // TODO: Load retention config (max count or max age)
+        // TODO: Query backups older than retention threshold
+        // TODO: Delete backup files from storage
+        // TODO: Delete backup records from DB
+        // TODO: Return count of deleted backups
+        todo!()
+    }
+}