Add CBOR and agent initiated WebSocket connections (#51, #490, #646, #845, etc)

- Add version exchange between hub and agent.
- Introduce ConnectionManager for managing WebSocket and SSH connections.
- Implement fingerprint generation and storage in agent.
- Create expiry map package to store universal tokens.
- Update config.yml configuration to include tokens.
- Enhance system management with new methods for handling system states and alerts.
- Update front-end components to support token / fingerprint management features.
- Introduce utility functions for token generation and hub URL retrieval.

Co-authored-by: nhas <jordanatararimu@gmail.com>

beszel/internal/agent/agent_test_helpers.go

@@ -0,0 +1,9 @@
+//go:build testing
+// +build testing
+
+package agent
+
+// TESTING ONLY: GetConnectionManager is a helper function to get the connection manager for testing.
+func (a *Agent) GetConnectionManager() *ConnectionManager {
+	return a.connectionManager
+}