Fix remaining overlay.remove bypassing winStack

Found 5 places that did overlay.remove() + history.back() directly
instead of going through winStack:
- Session detail recalculate/refresh
- Delete supplement
- Delete bike
- Delete goal marker
- Goal marker add button
- Compare session selection

All converted to: winStack.pop().close() + _skipPops + history.back()
No more direct overlay.remove() outside of winStack close handlers.

frontend/js/main.js

@@ -1921,8 +1921,9 @@ async function showGoalMarkersModal() {
       btn.onclick = async (e) => {
         e.stopPropagation();
         await DB.deleteGoalMarker(parseInt(btn.dataset.mid));
-        // Refresh modal
-        overlay.remove();
+        // Close and reopen modal
+        if (winStack.length > 0) winStack.pop().close();
+        _skipPops = 1;
         history.back();
         showGoalMarkersModal();
       };
@@ -1930,7 +1931,8 @@ async function showGoalMarkersModal() {
 
     // Add button
     overlay.querySelector("#gm-add").onclick = () => {
-      overlay.remove();
+      if (winStack.length > 0) winStack.pop().close();
+      _skipPops = 1;
       history.back();
       showAddGoalMarkerModal();
     };
@@ -2830,7 +2832,8 @@ async function showSessionDetail(sessionId) {
       recalcBtn.disabled = false;
       if (newStats) {
         // Close modal and reopen with fresh data
-        document.querySelector(".modal-overlay")?.remove();
+        if (winStack.length > 0) winStack.pop().close();
+        _skipPops = 1;
         history.back();
         showSessionDetail(sessionId);
       }
@@ -3010,7 +3013,8 @@ async function showCompareModal(sessionId, currentSession, currentPoints) {
       item.onclick = async () => {
         const compId = parseInt(item.dataset.sid);
         // Close this modal, open comparison view
-        overlay.remove();
+        if (winStack.length > 0) winStack.pop().close();
+        _skipPops = 1;
         history.back();
         await showComparisonView(sessionId, compId, currentSession, currentPoints);
       };
@@ -3323,7 +3327,8 @@ function showEditSupplementModal(existing) {
         delBtn.onclick = async (e) => {
           e.stopPropagation();
           await DB.deleteSupplement(existing.id);
-          document.querySelector(".modal-overlay")?.remove();
+          if (winStack.length > 0) winStack.pop().close();
+          _skipPops = 1;
           history.back();
           renderScreen("supplements");
         };
@@ -3730,7 +3735,8 @@ async function showBikeModal(bikeId) {
         delBtn.onclick = async (e) => {
           e.stopPropagation();
           await DB.deleteBike(bikeId);
-          document.querySelector(".modal-overlay")?.remove();
+          if (winStack.length > 0) winStack.pop().close();
+          _skipPops = 1;
           history.back();
           renderScreen("settings");
         };