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

config/default_config.yaml

@@ -0,0 +1,25 @@
+# Default configuration for Zynq XC7Z100 Flasher
+# Paths are relative to this config file's directory.
+
+# Vitis/Vivado installation path (where bootgen, impact, etc. reside)
+vitis_path: ""
+
+# Zynq device network settings
+zynq_ip: "192.168.100.11"
+tftp_upload_name: "z7bin"
+
+# Serial port settings
+serial_port: ""
+serial_baudrate: 115200
+
+# File paths (relative to config file directory)
+bin_path: ""
+elf_path: ""
+bit_path: ""
+
+# Reboot settings
+reboot_timeout: 30
+
+# Ping verification settings
+ping_timeout: 5
+ping_count: 3