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/hub/hub_test_helpers.go

@@ -0,0 +1,21 @@
+//go:build testing
+// +build testing
+
+package hub
+
+import "beszel/internal/hub/systems"
+
+// TESTING ONLY: GetSystemManager returns the system manager
+func (h *Hub) GetSystemManager() *systems.SystemManager {
+	return h.sm
+}
+
+// TESTING ONLY: GetPubkey returns the public key
+func (h *Hub) GetPubkey() string {
+	return h.pubKey
+}
+
+// TESTING ONLY: SetPubkey sets the public key
+func (h *Hub) SetPubkey(pubkey string) {
+	h.pubKey = pubkey
+}