chore(init): 初始化解忧商行项目并完成 Phase 0 基座

backend/internal/integrations/sms/unavailable.go

@@ -0,0 +1,25 @@
+package sms
+
+import "context"
+
+type UnavailableProvider struct {
+	err error
+}
+
+func NewUnavailableProvider(err error) *UnavailableProvider {
+	return &UnavailableProvider{err: err}
+}
+
+func (p *UnavailableProvider) SendLoginCode(ctx context.Context, phone string, code string) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+	if p.err != nil {
+		return p.err
+	}
+	return ErrProviderConfigInvalid
+}
+
+func (p *UnavailableProvider) SendTemplate(ctx context.Context, req TemplateRequest) error {
+	return p.SendLoginCode(ctx, req.Phone, "")
+}