feat: add Linux disk space monitoring support- add disk_linux.go using syscall.Statfs to retrieve disk info- update disk_other.go build tag to exclude both Windows and Linux

backend/internal/monitor/disk_linux.go

@@ -0,0 +1,28 @@
+//go:build linux
+
+package monitor
+
+import (
+	"os"
+	"syscall"
+)
+
+func getDiskSpaceGB() (float64, float64) {
+	wd, err := os.Getwd()
+	if err != nil {
+		return 0, 0
+	}
+
+	var stat syscall.Statfs_t
+	if err := syscall.Statfs(wd, &stat); err != nil {
+		return 0, 0
+	}
+
+	const gb = 1024.0 * 1024.0 * 1024.0
+	blockSize := uint64(stat.Bsize)
+
+	totalBytes := stat.Blocks * blockSize
+	freeBytes := stat.Bfree * blockSize
+
+	return float64(totalBytes) / gb, float64(freeBytes) / gb
+}

backend/internal/monitor/disk_other.go

@@ -1,4 +1,4 @@
-//go:build !windows
+//go:build !windows && !linux
 
 package monitor