sysinfo: advertise Ed25519 public key for opsbase TOFU enrollment

Include the agent's base64 Ed25519 public key in the `pk` field of the
sysinfo upload. opsbase (acting as the agent's api-server) has no rendezvous
server to learn the key from, so it pins this key trust-on-first-use on first
contact and verifies every later signed request against it.

This is the same keypair sign.rs already signs requests with. Vanilla
rustdesk servers ignore the unknown field, so the change is backward
compatible.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

vendor/rustdesk/src/hbbs_http/sync.rs

@@ -184,6 +184,15 @@ async fn start_hbbs_sync_async() {
                     v["version"] = json!(crate::VERSION);
                     v["id"] = json!(id);
                     v["uuid"] = json!(crate::encode64(hbb_common::get_uuid()));
+                    // opsbase enrollment: advertise our Ed25519 public key so the
+                    // server can pin it trust-on-first-use and verify our signed
+                    // requests. This is the same keypair `sign.rs` signs with and
+                    // rendezvous registers. Harmless on vanilla rustdesk servers,
+                    // which ignore unknown sysinfo fields.
+                    let (_sk, pk_bytes) = Config::get_key_pair();
+                    if !pk_bytes.is_empty() {
+                        v["pk"] = json!(crate::encode64(&pk_bytes));
+                    }
                     // Optional rebrand identity: `AGENT_NAME` / `AGENT_VERSION`
                     // are empty by default (vanilla rustdesk) and populated by
                     // OEM shells like hello-agent. We only stamp the field