feat(qs): 汽水音乐平台接入——匿名搜索/试听、抖音扫码登录、解密流代理

- sdk/qs 平台模块(安卓参数指纹匿名搜索)+ sdk/apis/qs 取流:
  匿名 30s 试听,登录态走签名 track_v2 + spade key AES-CTR 解密
- /login/qs/qr 抖音扫码登录(授权后 sessionid 解锁完整曲目)
- /stream/qs/:id 解密流代理,/url 返回的相对地址按请求 host 补全
- 回归测试覆盖 kw 双通道(VIP 真音频/降级链)与 qs 试听;start.bat 去掉
  SOURCE_ENABLED 直启

sdk/qs/crypto/protobuf.ts

@@ -0,0 +1,54 @@
+const WIRE_VARINT = 0;
+const WIRE_BYTES = 2;
+const WIRE_FIXED32 = 5;
+
+export class ProtobufWriter {
+    private readonly buf: number[] = [];
+
+    private writeVarint(value: number): this {
+        let v = value >>> 0;
+        while (v >= 0x80) {
+            this.buf.push((v & 0x7f) | 0x80);
+            v >>>= 7;
+        }
+        this.buf.push(v & 0x7f);
+        return this;
+    }
+
+    private writeKey(fieldNumber: number, wireType: number): this {
+        return this.writeVarint((fieldNumber << 3) | wireType);
+    }
+
+    varint(fieldNumber: number, value: number): this {
+        return this.writeKey(fieldNumber, WIRE_VARINT).writeVarint(value);
+    }
+
+    fixed32(fieldNumber: number, value: number): this {
+        this.writeKey(fieldNumber, WIRE_FIXED32);
+        const v = value >>> 0;
+        this.buf.push(v & 0xff, (v >>> 8) & 0xff, (v >>> 16) & 0xff, (v >>> 24) & 0xff);
+        return this;
+    }
+
+    bytes(fieldNumber: number, data: ArrayLike<number>): this {
+        this.writeKey(fieldNumber, WIRE_BYTES).writeVarint(data.length);
+        for (let i = 0; i < data.length; i++) {
+            this.buf.push(data[i]! & 0xff);
+        }
+        return this;
+    }
+
+    string(fieldNumber: number, value: string): this {
+        return this.bytes(fieldNumber, new TextEncoder().encode(value));
+    }
+
+    message(fieldNumber: number, build: (writer: ProtobufWriter) => void): this {
+        const sub = new ProtobufWriter();
+        build(sub);
+        return this.bytes(fieldNumber, sub.toBytes());
+    }
+
+    toBytes(): Uint8Array<ArrayBuffer> {
+        return Uint8Array.from(this.buf);
+    }
+}