P4: messages, topics, pubkey

Backend
- api/messages.rs covers send/pop/reply/status with an externally
  tagged MessageDestination enum that matches the daemon's
  {ip|pk: ...} body shape; pop_message uses an inflated request
  timeout to outlast the long-poll window
- api/topics.rs implements default action, topic CRUD, sources
  whitelist, and forward-socket get/set/remove. POST /topics ships
  the raw base64 string as the body (not JSON); path segments are
  percent-encoded inline (topics contain '/' and '+')
- api/pubkey.rs resolves an overlay IPv6 to a hex public key
- poller spawns a third long-poll loop on /messages?peek=false
  that fans every inbound message into a 200-deep ring buffer and
  emits messages://incoming for the UI

Frontend
- messages store: live inbox via the event, persisted outbox via
  tauri-plugin-store keyed under outbox.json
- ComposeMessage form: ip/pk toggle, optional UTF-8 topic and
  payload that get base64-encoded with a TextEncoder-based helper
- MessageList renders printable payloads decoded; binary payloads
  fall back to a "(N bytes binary)" hint
- Topics view: split layout with whitelist on the left, per-topic
  sources/forward editor on the right; default-action toggle is
  surfaced at the top

src-tauri/src/poller.rs

@@ -1,6 +1,8 @@
+use crate::api::messages::IncomingMessage;
 use crate::api::peers;
 use crate::sidecar::SidecarHandle;
 use parking_lot::Mutex;
+use std::collections::VecDeque;
 use std::sync::Arc;
 use std::time::Duration;
 use tauri::{AppHandle, Emitter};
@@ -9,10 +11,15 @@ use tracing::warn;
 
 const PEERS_INTERVAL: Duration = Duration::from_secs(3);
 const ROUTES_INTERVAL: Duration = Duration::from_secs(5);
+const INBOX_LONG_POLL_SECS: u64 = 30;
+const INBOX_RETRY_BACKOFF: Duration = Duration::from_secs(2);
+const INBOX_CAPACITY: usize = 200;
 
 pub struct Poller {
     peers_handle: Mutex<Option<JoinHandle<()>>>,
     routes_handle: Mutex<Option<JoinHandle<()>>>,
+    inbox_handle: Mutex<Option<JoinHandle<()>>>,
+    inbox: Mutex<VecDeque<IncomingMessage>>,
 }
 
 impl Poller {
@@ -20,30 +27,49 @@ impl Poller {
         Arc::new(Self {
             peers_handle: Mutex::new(None),
             routes_handle: Mutex::new(None),
+            inbox_handle: Mutex::new(None),
+            inbox: Mutex::new(VecDeque::with_capacity(INBOX_CAPACITY)),
         })
     }
 
-    /// Spawn the two background loops. Cancels any previously-running tasks
-    /// so consecutive `start_daemon` calls don't leak handles.
     pub fn start(self: &Arc<Self>, app: AppHandle, sidecar: Arc<SidecarHandle>) {
         self.stop();
         *self.peers_handle.lock() = Some(spawn_peers_loop(app.clone(), Arc::clone(&sidecar)));
-        *self.routes_handle.lock() = Some(spawn_routes_loop(app, sidecar));
+        *self.routes_handle.lock() = Some(spawn_routes_loop(app.clone(), Arc::clone(&sidecar)));
+        *self.inbox_handle.lock() = Some(spawn_inbox_loop(
+            app,
+            Arc::clone(&sidecar),
+            Arc::clone(self),
+        ));
     }
 
     pub fn stop(&self) {
-        if let Some(h) = self.peers_handle.lock().take() {
-            h.abort();
+        for slot in [&self.peers_handle, &self.routes_handle, &self.inbox_handle] {
+            if let Some(h) = slot.lock().take() {
+                h.abort();
+            }
         }
-        if let Some(h) = self.routes_handle.lock().take() {
-            h.abort();
+    }
+
+    pub fn inbox_snapshot(&self) -> Vec<IncomingMessage> {
+        self.inbox.lock().iter().cloned().collect()
+    }
+
+    pub fn clear_inbox(&self) {
+        self.inbox.lock().clear();
+    }
+
+    fn push_inbox(&self, msg: IncomingMessage) {
+        let mut buf = self.inbox.lock();
+        if buf.len() >= INBOX_CAPACITY {
+            buf.pop_front();
         }
+        buf.push_back(msg);
     }
 }
 
 fn spawn_peers_loop(app: AppHandle, sidecar: Arc<SidecarHandle>) -> JoinHandle<()> {
     tokio::spawn(async move {
-        // Tick once immediately so the UI doesn't wait the full interval.
         let mut first = true;
         loop {
             if !first {
@@ -87,3 +113,31 @@ fn spawn_routes_loop(app: AppHandle, sidecar: Arc<SidecarHandle>) -> JoinHandle<
         }
     })
 }
+
+fn spawn_inbox_loop(
+    app: AppHandle,
+    sidecar: Arc<SidecarHandle>,
+    me: Arc<Poller>,
+) -> JoinHandle<()> {
+    tokio::spawn(async move {
+        loop {
+            let Some(client) = sidecar.client() else {
+                break;
+            };
+            // Each iteration is a fresh long-poll. The daemon answers as
+            // soon as a message arrives, or returns an empty body / 204
+            // when the timeout window elapses.
+            match client.pop_message(false, INBOX_LONG_POLL_SECS, None).await {
+                Ok(Some(msg)) => {
+                    me.push_inbox(msg.clone());
+                    let _ = app.emit("messages://incoming", &msg);
+                }
+                Ok(None) => {} // window expired, loop
+                Err(e) => {
+                    warn!(error = %e, "inbox: pop_message failed");
+                    tokio::time::sleep(INBOX_RETRY_BACKOFF).await;
+                }
+            }
+        }
+    })
+}