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.

deploy/compose/docker-compose.remote-speaker.yaml

@@ -27,9 +27,7 @@ services:
     network_mode: host
     cap_add:
       - NET_ADMIN
-    sysctls:
-      net.ipv4.ip_forward: "1"
-      net.ipv6.conf.all.forwarding: "1"
+    # sysctls нельзя с network_mode: host — включите ip_forward на VPS (см. docs/remote-speakers.md)
     volumes:
       - bird_etc:/etc/bird
       - bird_run:/run/bird