fix(weixin): 扫码登录二维码真实可扫——前端生成QR(修坏图) + DecodeConfig容忍空config

weixin qrcode_img_content 是微信liteapp HTML页(非图片),后端fetch转base64只得<!doctype>→前端img坏图。
- 后端 login-qr 改返回 qrUrl(qrcode_img_content URL)+qrCode(原始qrcode),去掉坏 qrImage
- 前端用 qrcode 库从 qrUrl 生成真实二维码图片(微信扫https链接即开连接页), 新增 qrcode+@types/qrcode(纯UI依赖)
- DecodeConfig: nil config map 当空map解码(不报错), 否则 pending账号(空config)构建被跳过→未注册→登录端点404
- 测试更新(DecodeConfigNil/admin QR端点断言 qrUrl+qrCode)
- 另有 weixinAccountFor 裸weixin兜底(此前提交 d3b0921) 保证 accountId 命中
- 实测: login-qr 200{waiting, qrUrl=89}, 前端能看到可扫二维码
build/vet/test 全绿, 已部署.

internal/channel/adapter/adapter.go

@@ -83,8 +83,11 @@ var (
 // configuration as strongly typed structs. Unknown keys are ignored; missing
 // keys leave the corresponding zero value.
 func DecodeConfig(raw map[string]any, v any) error {
+	// A nil config map is treated as empty (decodes to the zero value), so a
+	// pending account with no keys yet (e.g. a weixin-ilink scan-login account the
+	// panel created before binding) builds with defaults rather than erroring.
 	if raw == nil {
-		return errors.New("adapter: nil config map")
+		raw = map[string]any{}
 	}
 	b, err := json.Marshal(raw)
 	if err != nil {

internal/channel/adapter/adapter_test.go

@@ -100,8 +100,13 @@ func TestDecodeConfig(t *testing.T) {
 func TestDecodeConfigNil(t *testing.T) {
 	t.Parallel()
 
+	// A nil config map is treated as empty (decodes to zero value), so a pending
+	// account with no keys yet builds with defaults rather than erroring.
 	var c struct{ Token string }
-	if err := DecodeConfig(nil, &c); err == nil {
-		t.Error("DecodeConfig(nil, ...) error = nil, want non-nil")
+	if err := DecodeConfig(nil, &c); err != nil {
+		t.Fatalf("DecodeConfig(nil, ...) error = %v, want nil (empty config)", err)
+	}
+	if c.Token != "" {
+		t.Fatalf("Token = %q, want empty zero value", c.Token)
 	}
 }