Implement device detection via libusb

[malikalhack]

Enumerate USB devices, match VID/PID for Hantek DSO-2250 (and family)

[malikalhack]

Task plan: Implement device detection via libusb

1. Add libusb dependency to CMake.

• Use pkg-config and libusb-1.0.
• Add a clear configuration error if only the runtime package is installed, not libusb-1.0-0-dev.
• Include the new USB source in the application target.
• Criteria: Clean Release build on Linux with libusb-1.0-0-dev.

2. Define a minimal public API for the USB module.

• Create usb/usb_device.h and usb/usb_device.cpp.
• API without UI/SDL/ImGui dependencies:
  • libusb initialization/deinitialization;
  • USB device enumeration;
  • search for a supported device;
  • structured output: not found, supported device found, libusb error.
• Currently, no interface opening, claim interface, or endpoint reading: these are separate future Stage 3 issues.

3. Implement a table of supported devices.

• Merge the VID/PID and model display name into a single static table.
• In the first step, add the Hantek DSO-2250 only after confirming the actual VID/PID.
• Implement family support: add a new model as a single entry in the table, without changing the scanning logic.

4. Implement search via libusb.

• Get the list via libusb_get_device_list().
• Read the libusb_device_descriptor of each device.
• Match idVendor/idProduct with the table.
• Ensure that the device list and context are freed on all paths.
• Convert errors to understandable statuses without crashing the application.

5, Attach the result to the current status bar.

• Perform a single device scan at startup.
• Display:
  • Hantek DSO-2250 detected if the device is found;
  • No supported device if none exists;
  • USB error: if libusb failed.
• Demo mode remains independent: detection will not automatically enable or disable demo mode for this task.

6. Verification

• Run make release.
• Launching without a supported device connected: the application opens, the UI does not freeze, and no device is displayed.
• Launching with the DSO-2250: the status shows the detected model and verified VID/PID.
• Add a short entry to HISTORY.md only after completion and successful verification.