feat(python): 完成 Python 全量迁移——剩余平台、登录通道与公共层修复

- 新增 5sing/apple/xm/me/qt/lr 平台包与取流实现（含 xm-sign、MissEvan 签名、蜻蜓 HMAC、Apple developer token）
- 新增 wy/kg/tx/lr 登录：扫码、手机号、账密（kg 20028 风控指纹）、cookie 绑定、kg/tx 续期
- request 层：保留多值 Set-Cookie；JSON body 紧凑化（修复 kg 网关验签）；直连不经系统代理（对齐 Node）
- 登录路由统一 Body(embed=True)，修复扫码轮询 422；lifespan 接入登录续期调度
- ruff/format/pyright 全绿；14 平台真实联网与 HTTP 路由验证通过

app/sdk/platforms/mg/music_search.py

@@ -0,0 +1,60 @@
+"""咪咕音乐搜索（对应 sdk/mg/musicSearch.ts）。
+
+search_all.do（Android_migu 参数），searchSwitch 控制返回类别 —— 歌曲/专辑/歌单三个
+子模块共用这一个接口，只切换 searchSwitch。
+上游对应 music-lib/migu/migu.go 的 (*Migu).Search。
+"""
+
+from __future__ import annotations
+
+import json
+import math
+from typing import Any
+
+from app.sdk.platforms.mg.util import build_url, convert_item_to_song, migu_get, parse_int
+
+SEARCH_ALL_URL = "http://pd.musicapp.migu.cn/MIGUM2.0/v1.0/content/search_all.do"
+
+
+def search_switch(kind: str) -> str:
+    """搜索开关：只开某一类（song/album/songlist），bestShow 保留最优推荐。"""
+    payload = {
+        "song": 1 if kind == "song" else 0,
+        "album": 1 if kind == "album" else 0,
+        "singer": 0,
+        "tagSong": 0,
+        "mvSong": 0,
+        "songlist": 1 if kind == "songlist" else 0,
+        "bestShow": 1,
+    }
+    return json.dumps(payload, ensure_ascii=False, separators=(",", ":"))
+
+
+async def search_all(text: str, kind: str, page: int = 1, limit: int = 20) -> Any:
+    url = build_url(
+        SEARCH_ALL_URL,
+        {
+            "ua": "Android_migu",
+            "version": "5.0.1",
+            "text": text,
+            "pageNo": page,
+            "pageSize": limit,
+            "searchSwitch": search_switch(kind),
+        },
+    )
+    return await migu_get(url)
+
+
+async def search(keyword: str, page: int = 1, limit: int = 20, retry_num: int = 0) -> dict[str, Any]:
+    body = await search_all(keyword, "song", page, limit)
+    data = body.get("songResultData") if isinstance(body, dict) else None
+    result = (data or {}).get("result") or []
+    songs = [song for item in result if (song := convert_item_to_song(item, True)) is not None]
+    total = parse_int((data or {}).get("totalCount")) or len(songs)
+    return {
+        "list": songs,
+        "allPage": max(1, math.ceil(total / limit)),
+        "total": total,
+        "limit": limit,
+        "source": "mg",
+    }