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

selective-vpn-api/app/dns_settings_state_upstreams_conf_store.go

@@ -0,0 +1,42 @@
+package app
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+
+	dnscfgpkg "selective-vpn-api/app/dnscfg"
+)
+
+func loadDNSUpstreamsConfFile() DNSUpstreams {
+	data, err := os.ReadFile(dnsUpstreamsConf)
+	if err != nil {
+		return dnscfgUpstreamsToApp(dnscfgLegacyDefaults())
+	}
+	pkgCfg := dnscfgpkg.ParseUpstreamsConf(string(data), dnscfgLegacyDefaults(), normalizeDNSUpstream)
+	return dnscfgUpstreamsToApp(pkgCfg)
+}
+
+func saveDNSUpstreamsConfFile(cfg DNSUpstreams) error {
+	pkgCfg := dnscfgpkg.NormalizeUpstreams(dnscfgUpstreamsFromApp(cfg), dnscfgLegacyDefaults(), normalizeDNSUpstream)
+	cfg = dnscfgUpstreamsToApp(pkgCfg)
+	content := dnscfgpkg.RenderUpstreamsConf(pkgCfg)
+
+	if err := os.MkdirAll(filepath.Dir(dnsUpstreamsConf), 0o755); err != nil {
+		return err
+	}
+	tmp := dnsUpstreamsConf + ".tmp"
+	if err := os.WriteFile(tmp, []byte(content), 0o644); err != nil {
+		return err
+	}
+	if err := os.Rename(tmp, dnsUpstreamsConf); err != nil {
+		return err
+	}
+
+	// Legacy JSON mirror for backward compatibility with older UI/runtime bits.
+	_ = os.MkdirAll(stateDir, 0o755)
+	if b, err := json.MarshalIndent(cfg, "", "  "); err == nil {
+		_ = os.WriteFile(dnsUpstreamsPath, b, 0o644)
+	}
+	return nil
+}