feat: Complete Phase 1 backend services and WebSocket/NATS bridge

Implements all remaining backend infrastructure for Corrosion platform.

Backend Services (5 new):
- license.rs: License validation, activation, check-in with NATS token generation
- map_manager.rs: Map upload/rotation with SHA-256 checksums, circular advancement
- health_checker.rs: Post-wipe verification with retry loop and backoff
- backup_manager.rs: Tar.gz backups with retention policy (last 10), recursive upload
- scheduler.rs: Tokio-cron integration for scheduled wipes with NATS events

WipeEngine Orchestration (wipe_engine.rs):
- execute_wipe(): Master orchestrator managing full lifecycle
- execute_pre_wipe(): Countdown warnings, backups, player kicks
- execute_wipe_actions(): Map/plugin deletion, seed rotation, Steam updates
- execute_post_wipe_verification(): Health checks with restart attempts
- execute_rollback(): Failure recovery with backup restore
- JSONB execution logs, NATS status events, service composition pattern

WebSocket/NATS Bridge (ws.rs):
- JWT authentication via query parameter
- License-scoped NATS subscriptions (corrosion.{license_id}.*)
- Bi-directional: NATS→WebSocket event forwarding, WebSocket→NATS publishing
- Axum 0.8 with ws feature, auto Ping/Pong handling

Panel Adapter Fixes:
- AMP/Pterodactyl/Companion adapters fully wired
- RCON command execution, file operations, Steam update triggers

Fixes:
- Added ws feature to Axum dependency
- Fixed Message::Text() type conversions (String→Utf8Bytes via .into())
- Fixed BackupInfo FromRow derive
- Fixed recursive async with Box::pin pattern
- Fixed async JobScheduler::new() constructor
- Removed manual WebSocket Ping/Pong handler

Compilation: 0 errors, 327 warnings (unused vars/functions)

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

backend/Cargo.toml

@@ -7,7 +7,7 @@ license = "Proprietary"
 
 [dependencies]
 # Web framework
-axum = { version = "0.8", features = ["macros", "multipart"] }
+axum = { version = "0.8", features = ["macros", "multipart", "ws"] }
 axum-extra = { version = "0.10", features = ["typed-header"] }
 tower = "0.5"
 tower-http = { version = "0.6", features = ["cors", "trace", "limit", "fs"] }
@@ -15,6 +15,7 @@ hyper = { version = "1", features = ["full"] }
 
 # Async runtime
 tokio = { version = "1", features = ["full"] }
+futures = "0.3"
 
 # Database
 sqlx = { version = "0.8", features = ["runtime-tokio-rustls", "postgres", "uuid", "chrono", "json", "migrate"] }
@@ -46,6 +47,7 @@ lettre = { version = "0.11", default-features = false, features = ["tokio1", "to
 
 # Scheduling
 tokio-cron-scheduler = "0.13"
+cron = "0.12"
 
 # Logging
 tracing = "0.1"
@@ -72,3 +74,9 @@ hex = "0.4"
 
 # HTTP types
 http = "1"
+
+# Byte buffers (used by NATS bridge)
+bytes = "1"
+
+# URL encoding (used by Pterodactyl adapter)
+urlencoding = "2"