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

selective-vpn-api/app/routes_cache_helpers_files.go

@@ -0,0 +1,48 @@
+package app
+
+import (
+	"os"
+	"strings"
+)
+
+func writeLinesFile(path string, lines []string) error {
+	if len(lines) == 0 {
+		return os.WriteFile(path, []byte{}, 0o644)
+	}
+	payload := strings.Join(lines, "\n")
+	if !strings.HasSuffix(payload, "\n") {
+		payload += "\n"
+	}
+	return os.WriteFile(path, []byte(payload), 0o644)
+}
+
+func readLinesFile(path string) ([]string, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	lines := make([]string, 0, 64)
+	for _, raw := range strings.Split(string(data), "\n") {
+		ln := strings.TrimSpace(raw)
+		if ln == "" {
+			continue
+		}
+		lines = append(lines, ln)
+	}
+	return lines, nil
+}
+
+func cacheCopyOrEmpty(src, dst string) error {
+	if err := copyFile(src, dst); err == nil {
+		return nil
+	}
+	return os.WriteFile(dst, []byte{}, 0o644)
+}
+
+func fileExists(path string) bool {
+	info, err := os.Stat(path)
+	if err != nil {
+		return false
+	}
+	return !info.IsDir()
+}