feat(federation): Phase 1 transport — signed event streams between instances

SensorEvent gets reply_to for directed routing. FederationConfig gains
peers (url + pubkey + subscriptions). New src/server/federation/ module
with SignedEvent (Ed25519 sign/verify) and FederationBridge (per-peer
outbound WS tasks with echo-safe seed_id filter and backoff reconnect).
Inbound /v1/federation/events handler verifies signatures before bus
injection. Bridge spawned in server::run() when federation.enabled.

src/core/memory/mod.rs

@@ -673,6 +673,7 @@ pub async fn execute_memory_command_with_context(
                     urgency: 0.1,
                     payload: None,
                     seed_id: None,
+                    reply_to: None,
                 });
             }
             Ok(format!("Wrote memory file: {}", path))
@@ -688,6 +689,7 @@ pub async fn execute_memory_command_with_context(
                     urgency: 0.1,
                     payload: None,
                     seed_id: None,
+                    reply_to: None,
                 });
             }
             Ok(format!("Appended to memory file: {}", path))
@@ -754,6 +756,7 @@ pub async fn execute_memory_command_with_context(
                     urgency: 0.2,
                     payload: None,
                     seed_id: None,
+                    reply_to: None,
                 });
             }
             Ok(format!("Deleted memory file: {}", path))