feat: initial Zynq XC7Z100 Flasher GUI project

Add cross-platform GUI application for programming Zynq devices
with step-by-step workflow:

- CustomTkinter GUI with dark/light theme support
- 4-step workflow: Check Env → Flash → Bootloader → Main Program
- YAML configuration with relative path resolution
- Serial monitoring and boot log parsing
- TFTP upload with CRC32 verification
- SSH/serial reboot management
- Vivado/Impact tool auto-detection

Project structure:
- app.py: Entry point
- src/: Core modules (config, flash, bitstream, tftp, serial, gui)
- config/: Default configuration template
- .flasher_env/: Python virtual environment

app.py

@@ -0,0 +1,22 @@
+"""Zynq XC7Z100 Flasher GUI — Entry Point."""
+
+import sys
+import os
+from pathlib import Path
+
+# Add src to path
+src_dir = Path(__file__).parent / "src"
+if str(src_dir) not in sys.path:
+    sys.path.insert(0, str(src_dir))
+
+from gui.main_window import MainWindow
+
+
+def main() -> None:
+    """Launch the Zynq Flasher GUI application."""
+    app = MainWindow()
+    app.mainloop()
+
+
+if __name__ == "__main__":
+    main()