feat: init sproutclaw-web — Go+Gin backend + React frontend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/services/models_config.go

@@ -0,0 +1,28 @@
+package services
+
+import (
+	"encoding/json"
+	"os"
+)
+
+// ReadModelsConfig reads models.json as a raw string.
+func ReadModelsConfig(path string) (string, error) {
+	data, err := os.ReadFile(path)
+	if os.IsNotExist(err) {
+		return "{}", nil
+	}
+	return string(data), err
+}
+
+// WriteModelsConfig validates JSON and writes models.json.
+func WriteModelsConfig(path, content string) error {
+	var v any
+	if err := json.Unmarshal([]byte(content), &v); err != nil {
+		return err
+	}
+	pretty, err := json.MarshalIndent(v, "", "  ")
+	if err != nil {
+		return err
+	}
+	return os.WriteFile(path, append(pretty, '\n'), 0o644)
+}