feat(api): enhance peer session management and documentation

- Added new fields to the API for tracking connected speakers and session states across multiple nodes, including `connected_speaker_id`, `connected_speaker_label`, `session_on_speakers`, `established_on_speakers`, and `session_mismatch`.
- Implemented a new endpoint for retrieving bird protocol sessions, enhancing the agent server functionality.
- Updated the OpenAPI documentation to reflect the new fields and query parameters, improving clarity for API consumers.
- Modified the frontend to display connected speaker information and session states, providing better visibility into peer connections.
- Updated deployment documentation to clarify the configuration requirements for enabling IP forwarding on VPS.

internal/birdfmt/peer_protocol.go

@@ -0,0 +1,16 @@
+package birdfmt
+
+import "strings"
+
+// PeerProtocolName returns the BIRD protocol name for a control-plane peer UUID.
+// Must stay in sync with pipeline peer rendering.
+func PeerProtocolName(peerID string) string {
+	s := strings.ReplaceAll(strings.TrimSpace(peerID), "-", "")
+	if len(s) > 16 {
+		s = s[:16]
+	}
+	if s == "" {
+		s = "x"
+	}
+	return "evobgp_p_" + s
+}