feat(market): portfolio groups — PORTFOLIO heading, clickable cards, icon + color

- Rename the portfolio heading "MY DRGX" -> "PORTFOLIO".
- Group cards are now clickable: clicking one opens the editor directly on that
  group (edit mode), with a hover highlight + hand cursor.
- PortfolioEntry gains an `icon` (project_icons wallet-icon name) and a `color`
  (packed IM_COL32 accent); both are persisted in settings.json.
- Editor edit-mode gains an icon picker (the same wallet icon set as the overview
  tab's address-label dialog, via material::project_icons) with a "None" option,
  and a color picker (preset accent palette + a default/no-color swatch).
- Group cards render the chosen icon to the left of the name and, when a color
  is set, a left accent bar + the icon tinted in that color.

Full-node + Lite build clean; ctest 1/1; hygiene clean. Rendering change — needs
a screenshot check of the Market portfolio + the editor.

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

src/config/settings.h

@@ -78,6 +78,8 @@ public:
     struct PortfolioEntry {
         std::string label;
         std::vector<std::string> addresses;
+        std::string icon;           // project_icons wallet-icon name; empty = no icon
+        unsigned int color = 0;     // packed IM_COL32 accent; 0 = theme default
     };
 
     // Theme