platform: modularize api/gui, add docs-tests-web foundation, and refresh root config

selective-vpn-api/app/transport_singbox_dns_migration_apply.go

@@ -0,0 +1,67 @@
+package app
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+func transportMaybeMigrateSingBoxDNSConfig(client TransportClient) (string, error) {
+	if client.Kind != TransportClientSingBox {
+		return "", nil
+	}
+	if !transportSingBoxDNSMigrationEnabled(client) {
+		return "", nil
+	}
+	path := transportSingBoxConfigPath(client)
+	if path == "" {
+		return "", nil
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return "", fmt.Errorf("read singbox config failed: %w", err)
+	}
+	var root map[string]any
+	if err := json.Unmarshal(data, &root); err != nil {
+		return "", fmt.Errorf("parse singbox config failed: %w", err)
+	}
+
+	changed, warnings := transportMigrateSingBoxDNSConfigMap(root)
+	if !changed {
+		if len(warnings) == 0 {
+			return "", nil
+		}
+		return "", errors.New(strings.Join(warnings, "; "))
+	}
+
+	backup := path + ".legacy-dns.bak"
+	if _, err := os.Stat(backup); os.IsNotExist(err) {
+		if writeErr := os.WriteFile(backup, data, 0o644); writeErr != nil {
+			return "", fmt.Errorf("write backup failed: %w", writeErr)
+		}
+	}
+
+	out, err := json.MarshalIndent(root, "", "  ")
+	if err != nil {
+		return "", fmt.Errorf("marshal migrated config failed: %w", err)
+	}
+	tmp := path + ".tmp"
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		return "", fmt.Errorf("ensure config dir failed: %w", err)
+	}
+	if err := os.WriteFile(tmp, append(out, '\n'), 0o644); err != nil {
+		return "", fmt.Errorf("write migrated config failed: %w", err)
+	}
+	if err := os.Rename(tmp, path); err != nil {
+		return "", fmt.Errorf("replace migrated config failed: %w", err)
+	}
+
+	msg := "singbox dns migrated to new server format"
+	if len(warnings) > 0 {
+		return msg, errors.New(strings.Join(warnings, "; "))
+	}
+	return msg, nil
+}