♻️ refactor(toolchain): replace impact/bootgen with xsct/program_flash + add fsbl

BREAKING: Replaces obsolete impact (ISE-era) and misused bootgen with
the correct Xilinx 2018.3–2023.2 toolchain.

Toolchain changes:
- vitis_checker: impact → xsct + program_flash + bootgen detection
- flash_programmer: bootgen/impact → program_flash (erase + program + verify)
- bitstream_programmer: impact → xsct fpga/dow (primary), vivado (fallback)
- Removed duplicated _get_impact_path() — now shared from vitis_checker

Config additions:
- fsbl_elf_path: FSBL ELF required by program_flash for QSPI init
- flash_type: QSPI mode (default: qspi-x4-single)

GUI additions:
- FSBL ELF file selector in Configuration panel
- Step 2 validates FSBL ELF is selected
- Step 1 now shows xsct/program_flash/bootgen in tool check

src/config_manager.py

@@ -23,6 +23,8 @@ DEFAULT_CONFIG: dict[str, Any] = {
     "bootloader_bit_path": "",
     "bootloader_elf_path": "",
     "bootloader_bin_path": "",
+    "fsbl_elf_path": "",
+    "flash_type": "qspi-x4-single",
     "firmware_bin_path": "",
     "reboot_timeout": 30,
     "ping_timeout": 5,
@@ -48,6 +50,8 @@ class Config:
     bootloader_bit_path: str = ""
     bootloader_elf_path: str = ""
     bootloader_bin_path: str = ""
+    fsbl_elf_path: str = ""
+    flash_type: str = "qspi-x4-single"
     firmware_bin_path: str = ""
     reboot_timeout: int = 30
     ping_timeout: int = 5
@@ -151,6 +155,8 @@ class Config:
             "bootloader_bit_path": self._relative_path(self.bootloader_bit_path),
             "bootloader_elf_path": self._relative_path(self.bootloader_elf_path),
             "bootloader_bin_path": self._relative_path(self.bootloader_bin_path),
+            "fsbl_elf_path": self._relative_path(self.fsbl_elf_path),
+            "flash_type": self.flash_type,
             "firmware_bin_path": self._relative_path(self.firmware_bin_path),
             "reboot_timeout": self.reboot_timeout,
             "ping_timeout": self.ping_timeout,