feat(chat): unread count + sidebar badge (Q1)

Track a per-conversation "last seen" watermark (message timestamp) on App:
- chatUnreadCount() sums incoming messages newer than each conversation's
  watermark; surfaced as SidebarStatus.chatUnreadCount → a badge on the Chat nav
  item (mirrors the History/Peers badges).
- Viewing a thread marks it seen (markChatConversationSeen while displayed).
- Baseline on load: existing stored messages are marked seen, so only messages
  that arrive while the app is open badge as unread.
- Wiped in resetChatSession so unread state never leaks across a wallet switch.
In-memory only (resets on app restart); persistence is a later refinement.

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

src/app.cpp

@@ -1503,6 +1503,7 @@ void App::render()
     ui::SidebarStatus sbStatus;
     sbStatus.peerCount   = static_cast<int>(state_.peers.size());
     sbStatus.miningActive = state_.mining.generate || state_.pool_mining.xmrig_running;
+    sbStatus.chatUnreadCount = chatUnreadCount();   // unread badge on the Chat nav item (Q1)
 
     // Load logo texture lazily on first frame (or after theme change)
     // Also reload when dark↔light mode changes so the correct variant shows

src/app.h

@@ -679,6 +679,17 @@ private:
     // no longer matches — so wallet A's seed can't be provisioned under wallet B via a stale job.
     int chat_session_generation_ = 0;
     bool chat_identity_unavailable_ = false;      // provisioning failed definitively (e.g. non-mnemonic wallet)
+    // Per-conversation "last seen" watermark (message timestamp) for unread tracking (Q1). Updated when a
+    // thread is viewed (markChatConversationSeen); wiped in resetChatSession so unread doesn't leak across
+    // wallets. In-memory only (resets on app restart).
+    std::map<std::string, std::int64_t> chat_seen_watermark_;
+public:
+    // Total unread incoming chat messages across all conversations (for the sidebar badge). 0 when the
+    // feature is off / no identity.
+    int chatUnreadCount() const;
+    // Mark a conversation read up to latestTs (called by the Chat tab while a thread is displayed).
+    void markChatConversationSeen(const std::string& cid, std::int64_t latestTs);
+private:
     // Provision the chat identity once the wallet seed is reachable+unlocked (per-tick, both
     // variants); derives via deriveChatIdentityFromSecret and wipes the secret. No-op when the
     // feature is off, already provisioned, in flight, or unavailable.

src/app_network.cpp

@@ -1227,6 +1227,26 @@ void App::processWalletSwitchRevert()
     daemon_restarting_ = false;   // the connect loop now restarts the previous wallet's daemon
 }
 
+int App::chatUnreadCount() const
+{
+    if (!chat::hushChatFeatureEnabledAtBuild() || !chat_service_.hasIdentity()) return 0;
+    int unread = 0;
+    const auto& store = chat_service_.store();
+    for (const auto& cid : store.conversationIds()) {
+        std::int64_t seen = 0;
+        const auto it = chat_seen_watermark_.find(cid);
+        if (it != chat_seen_watermark_.end()) seen = it->second;
+        for (const auto& m : store.conversation(cid))
+            if (m.direction == chat::ChatDirection::Incoming && m.timestamp > seen) ++unread;
+    }
+    return unread;
+}
+
+void App::markChatConversationSeen(const std::string& cid, std::int64_t latestTs)
+{
+    if (latestTs > 0) chat_seen_watermark_[cid] = latestTs;
+}
+
 void App::wipePendingTransactionHistoryCachePassphrase()
 {
     if (!pending_transaction_history_cache_passphrase_.empty()) {
@@ -2658,6 +2678,13 @@ void App::provisionChatIdentityFromSecret(std::string secret)
         chat_service_.setPersistence(&chat_db_);
         if (chat_db_.unlockWithSecret(trimmed)) {
             chat_service_.loadFromDatabase();
+            // Baseline unread: treat everything already in the store at load as read, so only messages
+            // that arrive while the app is open badge as unread (Q1).
+            const auto& store = chat_service_.store();
+            for (const auto& cid : store.conversationIds()) {
+                const auto msgs = store.conversation(cid);
+                if (!msgs.empty()) chat_seen_watermark_[cid] = msgs.back().timestamp;
+            }
         }
     } else {
         chat_identity_unavailable_ = true;
@@ -2677,6 +2704,7 @@ void App::resetChatSession()
     // Drop identity + decrypted plaintext in RAM, lock the seed-encrypted DB, re-arm provisioning.
     chat_service_.clearIdentity();
     chat_service_.store().clear();
+    chat_seen_watermark_.clear();  // unread state is per-wallet — don't leak it across a switch
     ui::ResetChatTab();  // wipe the chat UI's typed plaintext + selection so it can't leak into the next wallet
     chat_db_.lock();
     chat_identity_provisioned_ = false;

src/ui/sidebar.h

@@ -149,6 +149,7 @@ struct SidebarStatus {
     int  unconfirmedTxCount = 0;   // badge on History
     bool miningActive       = false; // green dot on Mining
     int  peerCount          = 0;   // badge on Peers
+    int  chatUnreadCount    = 0;   // badge on Chat (unread incoming messages)
     // Exit
     bool exitClicked        = false;
     // Branding logo (optional — loaded at startup)
@@ -715,6 +716,8 @@ inline bool RenderSidebar(NavPage& current, float sidebarWidth, float contentHei
                 dotOnly = true; badgeCol = Success();
             } else if (item.page == NavPage::Peers && status.peerCount > 0) {
                 badgeCount = status.peerCount;
+            } else if (item.page == NavPage::Chat && status.chatUnreadCount > 0) {
+                badgeCount = status.chatUnreadCount;
             }
 
             if (badgeCount > 0 || dotOnly) {

src/ui/windows/chat_tab.cpp

@@ -275,6 +275,7 @@ void RenderChatTab(App* app)
         for (const auto& c : convs) if (c.cid == s_selected_cid) { sel = &c; break; }
 
         if (sel) {
+            app->markChatConversationSeen(sel->cid, sel->lastTs);  // viewing the thread clears its unread (Q1)
             // Header: peer name + z-address.
             ImGui::PushFont(material::Type().subtitle1());
             ImGui::TextUnformatted(sel->peerName.c_str());