fix: add missing destructor definitions in .cpp files

- Added destructor definitions (= default) to all classes that had them declared in header but not defined
- Fixes 'undefined reference to destructor' linker errors across 30+ classes
- Covers services, UI components, and synchronizers

src/ui/richtexteditor.cpp

@@ -459,4 +459,5 @@ void RichTextEditor::modifyTableBorder() {
     QTextTableFormat fmt = m_currentTable->format();
     fmt.setBorder(border);
     m_currentTable->setFormat(fmt);
-}
+}
+RichTextEditor::~RichTextEditor() = default;