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/util/i18n.cpp

@@ -1117,9 +1117,12 @@ void I18n::loadBuiltinEnglish()
         strings_["market_no_price"] = "No price data";
         strings_["market_now"] = "Now";
         strings_["market_pct_shielded"] = "%.0f%% Shielded";
-        strings_["market_portfolio"] = "MY DRGX";
+        strings_["market_portfolio"] = "PORTFOLIO";
         strings_["portfolio_all_funds"] = "All funds";
         strings_["portfolio_manage"] = "Manage\xE2\x80\xA6";
+        strings_["portfolio_icon"] = "Icon";
+        strings_["portfolio_color"] = "Color";
+        strings_["portfolio_no_icon"] = "None";
         strings_["portfolio_manage_title"] = "Manage portfolio";
         strings_["portfolio_add_entry"] = "Add entry";
         strings_["portfolio_new_entry"] = "New entry";