fix: resolve "no backend available" libusb error on Windows

kneron_detect.py now prepends the install directory to PATH before
importing pyusb, so libusb-1.0.dll in the install dir is found.
DetectHardware() also sets PATH in the subprocess environment.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

edge-ai-platform/installer/app.go

@@ -559,6 +559,12 @@ func (inst *Installer) DetectHardware() ([]HardwareDevice, error) {
 	}
 
 	cmd := exec.Command(pythonPath, detectScript)
+	cmd.Dir = installDir
+	// Ensure libusb-1.0.dll can be found on Windows by adding install dir to PATH
+	cmd.Env = append(os.Environ(), fmt.Sprintf("PATH=%s;%s;%s",
+		installDir,
+		filepath.Join(installDir, "scripts"),
+		os.Getenv("PATH")))
 	out, err := cmd.CombinedOutput()
 	if err != nil {
 		return nil, fmt.Errorf("detection failed: %s — %w", string(out), err)

edge-ai-platform/scripts/kneron_detect.py

@@ -1,6 +1,18 @@
 """Kneron USB device detection — shared by install scripts and kneron_bridge.py"""
+import os
 import sys
 
+# On Windows, ensure libusb-1.0.dll can be found by pyusb.
+# The DLL may be in the install directory or scripts/ subdirectory.
+if sys.platform == "win32":
+    _script_dir = os.path.dirname(os.path.abspath(__file__))
+    _install_dir = os.path.dirname(_script_dir)
+    for _dir in [_install_dir, _script_dir]:
+        _dll = os.path.join(_dir, "libusb-1.0.dll")
+        if os.path.isfile(_dll):
+            os.environ["PATH"] = _dir + ";" + os.environ.get("PATH", "")
+            break
+
 try:
     import usb.core
 except ImportError: