fix: global blue highlight, Ctrl+F find bar with prev/next/close buttons

- Change QPalette::Highlight from theme.selection to theme.hover globally
- RcxEditor find: use SCI_SEARCHINTARGET + INDIC_COMPOSITIONTHICK indicator
  (selection rendering is disabled, so findFirst was invisible)
- Re-apply find indicators after applyDocument() refresh cycle
- Add prev/next/close buttons to find bars in both Reclass and C/C++ modes
- Buttons styled with hover/pressed states matching tab styling

src/editor.h

@@ -156,7 +156,9 @@ private:
     const NodeTree* m_disasmTree = nullptr;
 
     // ── Find bar ──
+    QWidget*   m_findBarContainer = nullptr;
     QLineEdit* m_findBar = nullptr;
+    long       m_findPos = 0;
     void showFindBar();
     void hideFindBar();