feat: Implement core functionality for DTC C/C++ IDE

- Added ProjectManager class to handle project operations including opening, closing, building, and running projects.
- Introduced SyntaxHighlighter class for syntax highlighting in C and C++ files.
- Developed TerminalWidget for command execution and output display.
- Created TextEditor with line numbering and auto-indentation features.
- Established main application entry point in main.cpp.
- Designed UI layout for MainWindow using Qt Designer.

include/FileTreeWidget.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include <QtWidgets/QTreeWidget>
+#include <QtWidgets/QTreeWidgetItem>
+#include <QtWidgets/QMenu>
+#include <QtCore/QFileSystemWatcher>
+#include <QtCore/QDir>
+
+class FileTreeWidget : public QTreeWidget
+{
+    Q_OBJECT
+
+public:
+    explicit FileTreeWidget(QWidget *parent = nullptr);
+    ~FileTreeWidget();
+
+    void setRootPath(const QString &path);
+    QString rootPath() const;
+    
+    void refreshTree();
+
+signals:
+    void fileSelected(const QString &filePath);
+    void fileDoubleClicked(const QString &filePath);
+    void directorySelected(const QString &dirPath);
+
+private slots:
+    void onItemClicked(QTreeWidgetItem *item, int column);
+    void onItemDoubleClicked(QTreeWidgetItem *item, int column);
+    void onCustomContextMenu(const QPoint &point);
+    void onDirectoryChanged(const QString &path);
+    void newFile();
+    void newFolder();
+    void deleteItem();
+    void renameItem();
+
+private:
+    void populateTree(const QString &path, QTreeWidgetItem *parent = nullptr);
+    void setupContextMenu();
+    QString getItemPath(QTreeWidgetItem *item) const;
+    bool isDirectory(QTreeWidgetItem *item) const;
+
+    QString m_rootPath;
+    QFileSystemWatcher *m_fileWatcher;
+    QMenu *m_contextMenu;
+    QTreeWidgetItem *m_contextItem;
+};