v3.42.9: Fix all timeout bugs and deadlocks

CRITICAL FIXES:
- Encryption detection false positive (IsBackupEncrypted returned true for ALL files)
- 12 cmd.Wait() deadlocks fixed with channel-based context handling
- TUI timeout bugs: 60s->10min for safety checks, 15s->60s for DB listing
- diagnose.go timeouts: 60s->5min for tar/pg_restore operations
- Panic recovery added to parallel backup/restore goroutines
- Variable shadowing fix in restore/engine.go

These bugs caused pg_dump backups to fail through TUI for months.

internal/cleanup/processes.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 	"sync"
 	"syscall"
+	"time"
 
 	"dbbackup/internal/logger"
 )
@@ -116,8 +117,11 @@ func KillOrphanedProcesses(log logger.Logger) error {
 
 // 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)
+	// Use pgrep for efficient process searching with timeout
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	cmd := exec.CommandContext(ctx, "pgrep", "-x", name)
 	output, err := cmd.Output()
 	if err != nil {
 		// Exit code 1 means no processes found (not an error)