✨ feat(manga,device): 漫画免签名兜底与 phone 注册身份选项

- /manga 设备池签名路线全部失败时自动降级 wkbrowser 免签名路线（materials/skeleton 三段策略收集原图直链，无需设备/签名/解密），响应附 source: wkbrowser
- 新增配置 fanqie.device_identity（默认 pad 保持现状；phone 对齐书源真机注册 payload：host_bit 64 + 补 hardware/device_device/fingerprint 字段）
- README 与 openapi.yaml 同步文档，新增 manga_fallback 解析测试

internal/fqapi/manga_fallback_test.go

@@ -0,0 +1,44 @@
+package fqapi
+
+import "testing"
+
+// TestCollectMangaFallbackURIs skeleton 顺序优先、web_uri/md5 取值与原图直链拼接
+func TestCollectMangaFallbackURIs(t *testing.T) {
+	payload := map[string]interface{}{
+		"materials": map[string]interface{}{
+			"img_1": map[string]interface{}{"data": map[string]interface{}{"web_uri": "novel-pic/aaa"}},
+			"img_2": map[string]interface{}{"data": map[string]interface{}{"web_uri": "/novel-pic/bbb"}},
+			"img_3": map[string]interface{}{"data": map[string]interface{}{"md5": "c0ffee"}},
+		},
+		"skeleton": map[string]interface{}{
+			"data": []interface{}{
+				map[string]interface{}{"elementInfo": "img_2"},
+				map[string]interface{}{"key": "img_1"},
+				map[string]interface{}{"id": "img_3"},
+			},
+		},
+	}
+
+	// 页序以 skeleton 引用顺序为准
+	want := []string{
+		"https://p6-novel.byteimg.com/origin/novel-pic/bbb",
+		"https://p6-novel.byteimg.com/origin/novel-pic/aaa",
+		"https://p6-novel.byteimg.com/origin/novel-pic/c0ffee",
+	}
+	got := collectMangaFallbackURIs(payload)
+	if len(got) != len(want) {
+		t.Fatalf("got %d 张 want %d 张: %v", len(got), len(want), got)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Errorf("[%d] got %s want %s", i, got[i], want[i])
+		}
+	}
+
+	// 无 skeleton 时退化为 materials key 末尾数字排序
+	delete(payload, "skeleton")
+	got = collectMangaFallbackURIs(payload)
+	if got[0] != want[1] || got[1] != want[0] {
+		t.Errorf("key 排序错误: %v", got)
+	}
+}