feat(companion): mesh party + Flare, keep-warm mesh, restored fast-start, UI fixes — 0.5.7

Combined session state from both agents (shared checkout):

- Mesh Party / Flare (experimental): phone-to-phone FIPS via party QR,
  Flare chat/beam on :5680, optional fixed UDP listen (2121); party-only
  phones get the baked-in Archipelago anchor so two bare phones reach
  each other across the internet, not just on a hotspot.
- Keep-warm mesh: a running healthy node survives app opens (restart
  only when dead or peers changed — peersDirty); requestMeshRestart for
  config changes. Cold start measured on-device: session in ~3.1s.
- Restored after regression: startup LAN-vs-mesh race (the party work
  was based on a pre-#114 file copy) and same-node routing (BTCPay/
  Pine/HA had returned to opening in the external browser).
- UI: top status-bar scrim removed (bottom-only bars); web app-session
  mobile bar is solid black — app theme colour no longer bleeds through
  the bar and its safe-area strip.

Served APK: 0.5.7 (vc27).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Android/rust/archy-fips-core/src/jni_glue.rs

@@ -76,8 +76,9 @@ pub extern "system" fn Java_com_archipelago_app_fips_FipsNative_deriveIdentity(
     out(&env, json)
 }
 
-/// Kotlin: `external fun start(secret: String, peersJson: String, tunFd: Int): String`
+/// Kotlin: `external fun start(secret: String, peersJson: String, tunFd: Int, listenPort: Int): String`
 /// Returns `{"npub": "...", "address": "..."}` or `{"error": "..."}`.
+/// `listenPort` 0 = outbound-only; non-zero = fixed UDP bind (party mode).
 #[no_mangle]
 pub extern "system" fn Java_com_archipelago_app_fips_FipsNative_start(
     mut env: JNIEnv,
@@ -85,11 +86,13 @@ pub extern "system" fn Java_com_archipelago_app_fips_FipsNative_start(
     secret: JString,
     peers_json: JString,
     tun_fd: jint,
+    listen_port: jint,
 ) -> jstring {
     init_logging();
     let secret = jstr(&mut env, &secret);
     let peers = jstr(&mut env, &peers_json);
-    let json = match mesh::start(&secret, &peers, tun_fd) {
+    let listen_port = u16::try_from(listen_port).unwrap_or(0);
+    let json = match mesh::start(&secret, &peers, tun_fd, listen_port) {
         Ok((npub, address)) => {
             serde_json::json!({ "npub": npub, "address": address }).to_string()
         }

Android/rust/archy-fips-core/src/mesh.rs

@@ -64,9 +64,14 @@ pub fn derive_identity(secret: &str) -> Result<IdentityInfo> {
 }
 
 /// Build the phone-side node config: leaf-only (never routes third-party
-/// traffic — battery), ephemeral outbound-only transports, no DNS responder,
-/// TUN enabled but attached to the VpnService fd rather than created.
-pub fn build_config(secret: &str, peers: Vec<PeerConfig>) -> Config {
+/// traffic — battery), no DNS responder, TUN enabled but attached to the
+/// VpnService fd rather than created.
+///
+/// `listen_port` 0 = ephemeral UDP (outbound-only, the default posture).
+/// Non-zero = fixed UDP bind so a nearby phone can dial us directly over a
+/// local link (party mode); leaf_only still guarantees we never carry
+/// third-party transit even while accepting an inbound link.
+pub fn build_config(secret: &str, peers: Vec<PeerConfig>, listen_port: u16) -> Config {
     let mut cfg = Config::default();
     cfg.node.identity.nsec = Some(secret.to_string());
     cfg.node.identity.persistent = false;
@@ -74,9 +79,8 @@ pub fn build_config(secret: &str, peers: Vec<PeerConfig>) -> Config {
     cfg.tun.enabled = true;
     cfg.tun.mtu = Some(1280);
     cfg.dns.enabled = false;
-    // Ephemeral UDP port: outbound dialing works, nothing predictable listens.
     cfg.transports.udp = TransportInstances::Single(UdpConfig {
-        bind_addr: Some("0.0.0.0:0".to_string()),
+        bind_addr: Some(format!("0.0.0.0:{listen_port}")),
         ..Default::default()
     });
     // TCP with no bind_addr = outbound-only (fallback when UDP is blocked).
@@ -94,7 +98,7 @@ pub fn parse_peers(peers_json: &str) -> Result<Vec<PeerConfig>> {
 /// Start the mesh node on the given TUN fd (from `VpnService.establish()`,
 /// detached — the node owns it from here). Returns (npub, ula) on success.
 /// Any previously running node is stopped first.
-pub fn start(secret: &str, peers_json: &str, tun_fd: i32) -> Result<(String, String)> {
+pub fn start(secret: &str, peers_json: &str, tun_fd: i32, listen_port: u16) -> Result<(String, String)> {
     stop();
 
     // Android hands the VpnService TUN fd over in non-blocking mode on some
@@ -111,7 +115,7 @@ pub fn start(secret: &str, peers_json: &str, tun_fd: i32) -> Result<(String, Str
     }
 
     let peers = parse_peers(peers_json)?;
-    let config = build_config(secret, peers);
+    let config = build_config(secret, peers, listen_port);
     let mut node = Node::new(config).map_err(|e| anyhow!("node init: {e}"))?;
     let npub = node.npub();
     let address = node.identity().address().to_ipv6().to_string();
@@ -247,7 +251,7 @@ mod tests {
     #[test]
     fn config_is_leaf_only_with_tun() {
         let id = generate_identity().unwrap();
-        let cfg = build_config(&id.secret_hex, vec![]);
+        let cfg = build_config(&id.secret_hex, vec![], 0);
         assert!(cfg.node.leaf_only);
         assert!(cfg.tun.enabled);
         assert_eq!(cfg.tun.mtu(), 1280);
@@ -255,4 +259,16 @@ mod tests {
         assert!(!cfg.transports.udp.is_empty());
         assert!(!cfg.transports.tcp.is_empty());
     }
+
+    #[test]
+    fn listen_port_sets_fixed_udp_bind() {
+        let id = generate_identity().unwrap();
+        let cfg = build_config(&id.secret_hex, vec![], 2121);
+        // Party mode keeps leaf_only — accepting a link is not routing transit.
+        assert!(cfg.node.leaf_only);
+        let TransportInstances::Single(udp) = &cfg.transports.udp else {
+            panic!("expected single UDP transport");
+        };
+        assert_eq!(udp.bind_addr.as_deref(), Some("0.0.0.0:2121"));
+    }
 }