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/MainWindow.h

@@ -0,0 +1,65 @@
+#pragma once
+
+#include <QtWidgets/QMainWindow>
+#include <QtWidgets/QMenuBar>
+#include <QtWidgets/QToolBar>
+#include <QtWidgets/QStatusBar>
+#include <QtWidgets/QSplitter>
+#include <QtWidgets/QTabWidget>
+#include <QtWidgets/QVBoxLayout>
+#include <QtWidgets/QHBoxLayout>
+#include <QtWidgets/QFileDialog>
+#include <QtWidgets/QMessageBox>
+#include <QtCore/QSettings>
+
+class TextEditor;
+class FileTreeWidget;
+class TerminalWidget;
+class ProjectManager;
+
+class MainWindow : public QMainWindow
+{
+    Q_OBJECT
+
+public:
+    MainWindow(QWidget *parent = nullptr);
+    ~MainWindow();
+
+private slots:
+    void newFile();
+    void openFile();
+    void saveFile();
+    void saveAsFile();
+    void openProject();
+    void buildProject();
+    void runProject();
+    void debugProject();
+    void showAbout();
+    void toggleTheme();
+
+private:
+    void setupUI();
+    void setupMenus();
+    void setupToolbar();
+    void setupStatusBar();
+    void connectSignals();
+    void loadSettings();
+    void saveSettings();
+
+    // UI Components
+    QSplitter *m_centralSplitter;
+    QSplitter *m_leftSplitter;
+    QTabWidget *m_editorTabs;
+    FileTreeWidget *m_fileTree;
+    TerminalWidget *m_terminal;
+    
+    // Managers
+    ProjectManager *m_projectManager;
+    
+    // Settings
+    QSettings *m_settings;
+    bool m_darkTheme;
+    
+    // Current file
+    QString m_currentFilePath;
+};