feat: add music source service — NetEase/QQ providers, unified interface, cookie auth

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/music/auth.ts

@@ -0,0 +1,35 @@
+import fs from "node:fs";
+import path from "node:path";
+
+export interface CookieStore {
+  save(platform: "netease" | "qq", cookie: string): void;
+  load(platform: "netease" | "qq"): string;
+}
+
+export function createCookieStore(cookieDir: string): CookieStore {
+  if (!fs.existsSync(cookieDir)) {
+    fs.mkdirSync(cookieDir, { recursive: true });
+  }
+
+  return {
+    save(platform: "netease" | "qq", cookie: string): void {
+      const filePath = path.join(cookieDir, `${platform}.json`);
+      fs.writeFileSync(
+        filePath,
+        JSON.stringify({ cookie, updatedAt: new Date().toISOString() }),
+        "utf-8"
+      );
+    },
+
+    load(platform: "netease" | "qq"): string {
+      const filePath = path.join(cookieDir, `${platform}.json`);
+      if (!fs.existsSync(filePath)) return "";
+      try {
+        const data = JSON.parse(fs.readFileSync(filePath, "utf-8"));
+        return data.cookie ?? "";
+      } catch {
+        return "";
+      }
+    },
+  };
+}