fix(history): show shielding moves as neutral "Shielded", not red "Sent"

A coinbase/transparent→shielded move (often auto-shield) was drawn with a red
"Sent" label and send arrow yet a green "+X" amount — an internally
contradictory row that reads as "money leaving" to anyone who auto-shielded. It
now renders as a neutral "Shielded" row (shield icon + the shielded accent
colour for label and amount), and since a shield is your own funds going
private — not a spend — it's excluded from the Sent card total and the Sent
filter (it merges into one row visible under "All").

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/mining_mode_toggle.cpp

@@ -120,7 +120,10 @@ void RenderMiningModeToggle(App* app, const WalletState& state, const MiningInfo
                 CancelMiningBenchmark(app, false);   // don't leave a pool benchmark running after switching to solo (L-11)
                 app->stopPoolMining();
             }
-            if (soloHov) ImGui::SetMouseCursor(ImGuiMouseCursor_Hand);
+            if (soloHov) {
+                ImGui::SetMouseCursor(ImGuiMouseCursor_Hand);
+                material::Tooltip("%s", TR("mining_solo_tip"));
+            }
         }
 
         ImGui::SetCursorScreenPos(poolMin);