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/commands.rs

@@ -1,6 +1,11 @@
 use crate::api::admin::NodeInfo;
+use crate::api::messages::{
+    IncomingMessage, MessageDestination, MessageStatus, PushMessageBody, PushMessageReceipt,
+};
 use crate::api::peers::{AggregatedStats, PeerInfo};
+use crate::api::pubkey::PubkeyLookup;
 use crate::api::routes::RoutesSnapshot;
+use crate::api::topics::DefaultAction;
 use crate::api::MyceliumClient;
 use crate::error::{AppError, AppResult};
 use crate::sidecar::SidecarConfig;
@@ -99,3 +104,146 @@ pub async fn peers_stats(state: State<'_, AppState>) -> AppResult<AggregatedStat
 pub async fn routes_snapshot(state: State<'_, AppState>) -> AppResult<RoutesSnapshot> {
     require_client(&state)?.routes_snapshot().await
 }
+
+// ─── Messages ────────────────────────────────────────────────────────────────
+
+#[tauri::command]
+pub async fn send_message(
+    state: State<'_, AppState>,
+    destination: MessageDestination,
+    topic_b64: String,
+    payload_b64: String,
+) -> AppResult<PushMessageReceipt> {
+    let body = PushMessageBody {
+        dst: destination,
+        topic: topic_b64,
+        payload: payload_b64,
+    };
+    require_client(&state)?.send_message(&body).await
+}
+
+#[tauri::command]
+pub async fn reply_message(
+    state: State<'_, AppState>,
+    id: String,
+    destination: MessageDestination,
+    topic_b64: String,
+    payload_b64: String,
+) -> AppResult<PushMessageReceipt> {
+    let body = PushMessageBody {
+        dst: destination,
+        topic: topic_b64,
+        payload: payload_b64,
+    };
+    require_client(&state)?.reply_message(&id, &body).await
+}
+
+#[tauri::command]
+pub async fn message_status(state: State<'_, AppState>, id: String) -> AppResult<MessageStatus> {
+    require_client(&state)?.message_status(&id).await
+}
+
+#[tauri::command]
+pub fn inbox_messages(state: State<'_, AppState>) -> Vec<IncomingMessage> {
+    state.poller.inbox_snapshot()
+}
+
+#[tauri::command]
+pub fn inbox_clear(state: State<'_, AppState>) {
+    state.poller.clear_inbox();
+}
+
+// ─── Topics ──────────────────────────────────────────────────────────────────
+
+#[tauri::command]
+pub async fn topics_default_get(state: State<'_, AppState>) -> AppResult<DefaultAction> {
+    require_client(&state)?.topics_default_get().await
+}
+
+#[tauri::command]
+pub async fn topics_default_set(state: State<'_, AppState>, accept: bool) -> AppResult<()> {
+    require_client(&state)?
+        .topics_default_set(&DefaultAction { accept })
+        .await
+}
+
+#[tauri::command]
+pub async fn topics_list(state: State<'_, AppState>) -> AppResult<Vec<String>> {
+    require_client(&state)?.topics_list().await
+}
+
+#[tauri::command]
+pub async fn topic_add(state: State<'_, AppState>, topic_b64: String) -> AppResult<()> {
+    if topic_b64.trim().is_empty() {
+        return Err(AppError::BadInput("topic must not be empty".into()));
+    }
+    require_client(&state)?.topic_add(topic_b64.trim()).await
+}
+
+#[tauri::command]
+pub async fn topic_remove(state: State<'_, AppState>, topic_b64: String) -> AppResult<()> {
+    require_client(&state)?.topic_remove(&topic_b64).await
+}
+
+#[tauri::command]
+pub async fn topic_sources_list(
+    state: State<'_, AppState>,
+    topic_b64: String,
+) -> AppResult<Vec<String>> {
+    require_client(&state)?.topic_sources_list(&topic_b64).await
+}
+
+#[tauri::command]
+pub async fn topic_source_add(
+    state: State<'_, AppState>,
+    topic_b64: String,
+    subnet: String,
+) -> AppResult<()> {
+    require_client(&state)?
+        .topic_source_add(&topic_b64, &subnet)
+        .await
+}
+
+#[tauri::command]
+pub async fn topic_source_remove(
+    state: State<'_, AppState>,
+    topic_b64: String,
+    subnet: String,
+) -> AppResult<()> {
+    require_client(&state)?
+        .topic_source_remove(&topic_b64, &subnet)
+        .await
+}
+
+#[tauri::command]
+pub async fn topic_forward_get(
+    state: State<'_, AppState>,
+    topic_b64: String,
+) -> AppResult<Option<String>> {
+    require_client(&state)?.topic_forward_get(&topic_b64).await
+}
+
+#[tauri::command]
+pub async fn topic_forward_set(
+    state: State<'_, AppState>,
+    topic_b64: String,
+    socket_path: String,
+) -> AppResult<()> {
+    require_client(&state)?
+        .topic_forward_set(&topic_b64, &socket_path)
+        .await
+}
+
+#[tauri::command]
+pub async fn topic_forward_remove(state: State<'_, AppState>, topic_b64: String) -> AppResult<()> {
+    require_client(&state)?
+        .topic_forward_remove(&topic_b64)
+        .await
+}
+
+// ─── Pubkey ──────────────────────────────────────────────────────────────────
+
+#[tauri::command]
+pub async fn lookup_pubkey(state: State<'_, AppState>, ip: String) -> AppResult<PubkeyLookup> {
+    require_client(&state)?.lookup_pubkey(&ip).await
+}