Standardize TODO/FIXME comments to Doxygen \todo format

Convert informal TODO and FIXME comments to Doxygen-recognized
      \todo format.

      - // TODO comments → //! \todo ...
      - // FIXME comments → //! \todo ...
      - /** @todo ... */ blocks → //! \todo ...
      - @brief TODO: placeholders → //! \todo (moved outside doc blocks)

cockatrice/src/interface/layouts/flow_layout.h

@@ -4,6 +4,7 @@
  * @brief A QLayout subclass that arranges child widgets in wrapping rows (horizontal flow)
  *        or wrapping columns (vertical flow).
  */
+//! \todo Document this file.
 
 #ifndef FLOW_LAYOUT_H
 #define FLOW_LAYOUT_H

cockatrice/src/interface/layouts/overlap_layout.cpp

@@ -223,7 +223,7 @@ void OverlapLayout::setGeometry(const QRect &rect)
         const int yPos = rect.top() + currentRow * (maxItemHeight - overlapOffsetHeight);
         item->setGeometry(QRect(xPos, yPos, maxItemWidth, maxItemHeight));
 
-        // TODO: Figure this out properly or maybe adjust size hint to account for this?
+        //! \todo Figure this out properly or maybe adjust size hint to account for this.
         // Update row and column indices based on the layout direction.
         if (overlapDirection == Qt::Horizontal) {
             currentColumn++;

cockatrice/src/interface/layouts/overlap_layout.h

@@ -1,8 +1,8 @@
 /**
  * @file overlap_layout.h
  * @ingroup UI
- * @brief TODO: Document this.
  */
+//! \todo Document this file.
 
 #ifndef OVERLAP_LAYOUT_H
 #define OVERLAP_LAYOUT_H