Fix: MySQL/MariaDB socket authentication - remove hardcoded -h flag for localhost

Issue: MySQL/MariaDB functions always used '-h hostname' flag, which can cause
issues with Unix socket authentication when connecting to localhost.

Similar to PostgreSQL peer authentication, MySQL prefers Unix socket connections
for localhost rather than TCP connections. Using '-h localhost' forces TCP which
may fail with socket-based authentication configurations.

Fixed locations:
1. internal/restore/safety.go:
   - checkMySQLDatabaseExists() - now conditionally adds -h flag
   - listMySQLUserDatabases() - now conditionally adds -h flag

2. cmd/placeholder.go:
   - mysqlRestoreCommand() - now conditionally adds -h flag

Pattern applied (consistent with PostgreSQL fixes):
- Skip -h flag when host is localhost, 127.0.0.1, or empty
- Only add -h flag for actual remote hosts
- Allows mysql client to use Unix socket connection for local access

This ensures MySQL/MariaDB operations work correctly with both:
- Socket authentication (localhost via Unix socket)
- Password authentication (remote hosts via TCP)

cmd/placeholder.go

@@ -730,12 +730,17 @@ func containsSQLKeywords(content string) bool {
 }
 
 func mysqlRestoreCommand(archivePath string, compressed bool) string {
-	parts := []string{
+	parts := []string{"mysql"}
-		"mysql",
+	
-		"-h", cfg.Host,
+	// Only add -h flag if host is not localhost (to use Unix socket)
+	if cfg.Host != "localhost" && cfg.Host != "127.0.0.1" && cfg.Host != "" {
+		parts = append(parts, "-h", cfg.Host)
+	}
+	
+	parts = append(parts,
 		"-P", fmt.Sprintf("%d", cfg.Port),
 		"-u", cfg.User,
-	}
+	)
 
 	if cfg.Password != "" {
 		parts = append(parts, fmt.Sprintf("-p'%s'", cfg.Password))

internal/restore/safety.go

@@ -326,13 +326,18 @@ func (s *Safety) checkPostgresDatabaseExists(ctx context.Context, dbName string)
 
 // checkMySQLDatabaseExists checks if MySQL database exists
 func (s *Safety) checkMySQLDatabaseExists(ctx context.Context, dbName string) (bool, error) {
-	cmd := exec.CommandContext(ctx,
+	args := []string{
-		"mysql",
-		"-h", s.cfg.Host,
 		"-P", fmt.Sprintf("%d", s.cfg.Port),
 		"-u", s.cfg.User,
 		"-e", fmt.Sprintf("SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME='%s'", dbName),
-	)
+	}
+	
+	// Only add -h flag if host is not localhost (to use Unix socket)
+	if s.cfg.Host != "localhost" && s.cfg.Host != "127.0.0.1" && s.cfg.Host != "" {
+		args = append([]string{"-h", s.cfg.Host}, args...)
+	}
+	
+	cmd := exec.CommandContext(ctx, "mysql", args...)
 
 	if s.cfg.Password != "" {
 		cmd.Env = append(os.Environ(), fmt.Sprintf("MYSQL_PWD=%s", s.cfg.Password))
@@ -405,14 +410,19 @@ func (s *Safety) listMySQLUserDatabases(ctx context.Context) ([]string, error) {
 	// Exclude system databases
 	query := "SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME NOT IN ('information_schema', 'mysql', 'performance_schema', 'sys') ORDER BY SCHEMA_NAME"
 	
-	cmd := exec.CommandContext(ctx,
+	args := []string{
-		"mysql",
-		"-h", s.cfg.Host,
 		"-P", fmt.Sprintf("%d", s.cfg.Port),
 		"-u", s.cfg.User,
 		"-N", // Skip column names
 		"-e", query,
-	)
+	}
+	
+	// Only add -h flag if host is not localhost (to use Unix socket)
+	if s.cfg.Host != "localhost" && s.cfg.Host != "127.0.0.1" && s.cfg.Host != "" {
+		args = append([]string{"-h", s.cfg.Host}, args...)
+	}
+	
+	cmd := exec.CommandContext(ctx, "mysql", args...)
 
 	if s.cfg.Password != "" {
 		cmd.Env = append(os.Environ(), fmt.Sprintf("MYSQL_PWD=%s", s.cfg.Password))