fix(chat): un-hide on lite receives + scope the contact picker per wallet

Review of fc414ee found two issues:

- HIGH: the lite variant harvests chat via ingestLiteChatMemos, which called
  ingest() without the newIncomingCids out-param — so the un-hide never ran and a
  hidden conversation stayed hidden PERMANENTLY on new messages (chat is default-ON
  and fully supported in Lite), breaking the "a new message brings it back"
  invariant. Wire the same un-hide + off-tab toast into the lite path.

- LOW: the new-conversation contact picker listed every z-address contact,
  ignoring the per-wallet scope the Contacts tab enforces — leaking another
  wallet's scoped contact into this wallet's picker. Apply the same scope test
  (global + legacy fail open; "w:" scopes match the active wallet).

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

src/app_network.cpp

@@ -3147,7 +3147,22 @@ void App::ingestLiteChatMemos(const wallet::LiteWalletAppRefreshModel& model)
         auto extracted = chat::extractHushChatTransactionMetadata(entry.second, true);
         for (auto& meta : extracted.metadata) metadata.push_back(std::move(meta));
     }
-    if (!metadata.empty()) chat_service_.ingest(metadata, txTimestamps, std::time(nullptr));
+    if (!metadata.empty()) {
+        std::vector<std::string> newChatCids;
+        chat_service_.ingest(metadata, txTimestamps, std::time(nullptr), &newChatCids);
+        // Mirror the full-node paths: a new incoming message un-hides a hidden conversation (you can't
+        // un-receive), and a non-muted new message toasts when we're off the Chat tab.
+        if (settings_) {
+            bool unhid = false;
+            for (const auto& cid : newChatCids)
+                if (settings_->isChatHidden(cid)) { settings_->setChatHidden(cid, false); unhid = true; }
+            if (unhid) settings_->save();
+        }
+        if (current_page_ != ui::NavPage::Chat &&
+            std::any_of(newChatCids.begin(), newChatCids.end(),
+                        [this](const std::string& cid){ return !(settings_ && settings_->isChatMuted(cid)); }))
+            ui::Notifications::instance().info(TR("chat_new_message_toast"));
+    }
 }
 
 bool App::lockLiteWallet()