fix(market): portfolio modal — hover assert, cut-off footer, plain heading, FX bleed, bigger delete icon

- Fix the ImGui error on hovering a group row: the per-row delete was an
  overlapping InvisibleButton + SetCursorScreenPos over the row Selectable. Replace
  it with a manual IsMouseHoveringRect / IsMouseClicked hit-test (no overlapping
  ImGui item, no cursor manipulation).
- Delete icon is larger (iconMed) and inset from the row edge (spacingMd).
- Footer no longer clipped: reserve 56px for the 40px buttons + separator.
- Manage-portfolio heading is now plain text (h6) with no title-bar background or
  divider — content floats on the backdrop.
- Sidebar theme-effect borders no longer bleed through the overlay: suppress panel
  theme-effects frame-wide (RAII guard in App::render via ui::PortfolioEditorActive)
  while the modal is open, instead of only during the market render.

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

src/ui/windows/market_tab.h

@@ -15,5 +15,9 @@ namespace ui {
  */
 void RenderMarketTab(App* app);
 
+// True while the full-window Manage-portfolio modal is open (used to suppress panel theme-effects
+// frame-wide so their foreground borders don't bleed over the overlay).
+bool PortfolioEditorActive();
+
 } // namespace ui
 } // namespace dragonx