Add comprehensive process cleanup on TUI exit

- Created internal/cleanup package for orphaned process management
- KillOrphanedProcesses(): Finds and kills pg_dump, pg_restore, gzip, pigz
- killProcessGroup(): Kills entire process groups (handles pipelines)
- Pass parent context through all TUI operations (backup/restore inherit cancellation)
- Menu cancel now kills all child processes before exit
- Fixed context chain: menu.ctx → backup/restore operations
- No more zombie processes when user quits TUI mid-operation

Context chain:
- signal.NotifyContext in main.go → menu.ctx
- menu.ctx → backup_exec.ctx, restore_exec.ctx
- Child contexts inherit cancellation via context.WithTimeout(parentCtx)
- All exec.CommandContext use proper parent context

Prevents: Orphaned pg_dump/pg_restore eating CPU/disk after TUI quit

internal/cleanup/processes.go

@@ -0,0 +1,138 @@
+package cleanup
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"dbbackup/internal/logger"
+)
+
+// KillOrphanedProcesses finds and kills any orphaned pg_dump, pg_restore, gzip, or pigz processes
+func KillOrphanedProcesses(log logger.Logger) error {
+	processNames := []string{"pg_dump", "pg_restore", "gzip", "pigz", "gunzip"}
+	
+	myPID := os.Getpid()
+	var killed []string
+	var errors []error
+	
+	for _, procName := range processNames {
+		pids, err := findProcessesByName(procName, myPID)
+		if err != nil {
+			log.Warn("Failed to search for processes", "process", procName, "error", err)
+			continue
+		}
+		
+		for _, pid := range pids {
+			if err := killProcessGroup(pid); err != nil {
+				errors = append(errors, fmt.Errorf("failed to kill %s (PID %d): %w", procName, pid, err))
+			} else {
+				killed = append(killed, fmt.Sprintf("%s (PID %d)", procName, pid))
+			}
+		}
+	}
+	
+	if len(killed) > 0 {
+		log.Info("Cleaned up orphaned processes", "count", len(killed), "processes", strings.Join(killed, ", "))
+	}
+	
+	if len(errors) > 0 {
+		return fmt.Errorf("some processes could not be killed: %v", errors)
+	}
+	
+	return nil
+}
+
+// findProcessesByName returns PIDs of processes matching the given name
+func findProcessesByName(name string, excludePID int) ([]int, error) {
+	// Use pgrep for efficient process searching
+	cmd := exec.Command("pgrep", "-x", name)
+	output, err := cmd.Output()
+	if err != nil {
+		// Exit code 1 means no processes found (not an error)
+		if exitErr, ok := err.(*exec.ExitError); ok && exitErr.ExitCode() == 1 {
+			return []int{}, nil
+		}
+		return nil, err
+	}
+	
+	var pids []int
+	lines := strings.Split(strings.TrimSpace(string(output)), "\n")
+	for _, line := range lines {
+		if line == "" {
+			continue
+		}
+		
+		pid, err := strconv.Atoi(line)
+		if err != nil {
+			continue
+		}
+		
+		// Don't kill our own process
+		if pid == excludePID {
+			continue
+		}
+		
+		pids = append(pids, pid)
+	}
+	
+	return pids, nil
+}
+
+// killProcessGroup kills a process and its entire process group
+func killProcessGroup(pid int) error {
+	// First try to get the process group ID
+	pgid, err := syscall.Getpgid(pid)
+	if err != nil {
+		// Process might already be gone
+		return nil
+	}
+	
+	// Kill the entire process group (negative PID kills the group)
+	// This catches pipelines like "pg_dump | gzip"
+	if err := syscall.Kill(-pgid, syscall.SIGTERM); err != nil {
+		// If SIGTERM fails, try SIGKILL
+		syscall.Kill(-pgid, syscall.SIGKILL)
+	}
+	
+	// Also kill the specific PID in case it's not in a group
+	syscall.Kill(pid, syscall.SIGTERM)
+	
+	return nil
+}
+
+// SetProcessGroup sets the current process to be a process group leader
+// This should be called when starting external commands to ensure clean termination
+func SetProcessGroup(cmd *exec.Cmd) {
+	cmd.SysProcAttr = &syscall.SysProcAttr{
+		Setpgid: true,
+		Pgid:    0, // Create new process group
+	}
+}
+
+// KillCommandGroup kills a command and its entire process group
+func KillCommandGroup(cmd *exec.Cmd) error {
+	if cmd.Process == nil {
+		return nil
+	}
+	
+	pid := cmd.Process.Pid
+	
+	// Get the process group ID
+	pgid, err := syscall.Getpgid(pid)
+	if err != nil {
+		// Process might already be gone
+		return nil
+	}
+	
+	// Kill the entire process group
+	if err := syscall.Kill(-pgid, syscall.SIGTERM); err != nil {
+		// If SIGTERM fails, use SIGKILL
+		syscall.Kill(-pgid, syscall.SIGKILL)
+	}
+	
+	return nil
+}