Speed Dial: replace tile monograms with native SVG icons

Tiles previously rendered a colored monogram (title/source initials plus an ordinal) with a per-id hue. Show the matching native SVG icon instead:

- AppAction/NativeCommand gain an `icon` field; commands get a curated key->icon table and settings inherit their group header's icon.
- Notebook tracks each page's resource icon name and reports it in tab_options(), so the tab picker can show it too.
- Searcher records the group icon so settings keep it through search.
- Web tile rendering swaps monogramFor/hue for an <img>; drop the now-unused hue/text CSS vars. Add a test asserting every non-empty icon resolves to a shipped SVG.

src/slic3r/GUI/Notebook.hpp

@@ -33,6 +33,8 @@ public:
     void SetPageText(size_t n, const wxString& strText);
     void SetCompact(size_t n, bool compact); // ORCA
     wxString GetPageText(size_t n) const;
+    // Resource name the page was inserted with (empty for plugin pages, which pass a wxBitmap).
+    const std::string& GetPageIcon(size_t n) const { return m_pageIcons[n]; }
     wxFlexGridSizer* GetBtnsSizer(){return m_buttons_sizer;}; // ORCA
     // ORCA: a companion widget shown right after the tab buttons (before any side_tools), e.g.
     // an overflow indicator. Pass nullptr to remove it; ownership stays with the caller.
@@ -47,6 +49,7 @@ private:
     int                             m_btn_margin;
     int                             m_line_margin;
     std::vector<wxString>           m_pageLabels; // ORCA
+    std::vector<std::string>        m_pageIcons;  // ORCA: resource icon name per page, plugin pages empty
     wxWindow*                       m_overflow_button{nullptr}; // ORCA
 };
 
@@ -241,6 +244,13 @@ public:
         return GetBtnsListCtrl()->GetPageText(n);
     }
 
+    // Resource icon name the page was inserted with; empty for pages added with a wxBitmap.
+    std::string GetPageIcon(size_t n) const
+    {
+        wxCHECK_MSG(n < GetPageCount(), std::string(), wxS("Invalid page"));
+        return GetBtnsListCtrl()->GetPageIcon(n);
+    }
+
     virtual bool SetPageImage(size_t WXUNUSED(n), int WXUNUSED(imageId)) override
     {
         return false;