fix: 强化 SSRF 防护、修复代理链路安全漏洞与代码质量问题

基于 Gemini Code Assist 审查建议，对代理链路进行全面安全加固与代码优化。

- [新增] `src/lib/server/ssrf.ts`: 使用 `dns.promises.lookup` 进行真实 IP 解析，
  替代原有的正则匹配，防御 DNS 重绑定、非十进制 IP 等绕过手段
- [新增] 为 `proxy/vod/m3u8`、`proxy/vod/key`、`video-proxy` 三个接口补齐 SSRF 校验，
  此前仅 `proxy-m3u8` 和 `proxy/vod/segment` 有防护
- [删除] `utils.ts` 中已弃用的 `isValidUrlForProxy` 函数

- 所有代理接口统一强制 SSRF 校验，不再仅限于 `source=directplay`

- 修复 `proxy/vod/segment` 中 `isCancelled` 为 `const` 导致流取消信号失效的问题
- 修复 `proxy-m3u8/route.ts` 中导入不存在的函数(`extractResolutionFromM3u8`, `filterAdsFromM3U8Default`, `resolveM3u8Links`)的构建错误
- 修复直链直连模式下 `fetchCurrentSourceVideoInfo` 使用 HLS.js (XHR) 探测视频分辨率
  触发 CORS 误报的问题，改为直接跳过探测
- 移除 `proxy/vod/segment` 中未使用的 `NextRequest` 导入

- [新增] `src/lib/server/proxy-headers.ts`: 抽取 CORS 响应头为共享工具函数，
  消除 `proxy/vod/segment`、`proxy/vod/key`、`proxy/vod/m3u8` 中重复代码
- 统一使用 `DIRECT_PLAY_SOURCE` 常量替代硬编码 `'directplay'` 字符串

- `src/lib/server/ssrf.ts`
- `src/lib/server/proxy-headers.ts`

- `/app/api/proxy-m3u8/route`
- `/app/api/proxy/vod/key/route`
- `/app/api/proxy/vod/m3u8/route`
- `/app/api/proxy/vod/segment/route`
- `/app/api/video-proxy/route`
- `/app/play/page`x
- `/lib/utils`

src/app/api/proxy/vod/key/route.ts

@@ -3,6 +3,8 @@
 import { NextResponse } from "next/server";
 
 import { getConfig } from "@/lib/config";
+import { validateProxyUrlServerSide } from '@/lib/server/ssrf';
+import { buildProxyStreamHeaders } from '@/lib/server/proxy-headers';
 
 export const runtime = 'nodejs';
 
@@ -33,6 +35,13 @@ export async function GET(request: Request) {
 
   try {
     const decodedUrl = decodeURIComponent(url);
+
+    // 安全校验：防 SSRF 拦截请求内网或非法 URL
+    const isSafeUrl = await validateProxyUrlServerSide(decodedUrl);
+    if (!isSafeUrl) {
+      return NextResponse.json({ error: 'Proxy request to local or invalid network is forbidden' }, { status: 403 });
+    }
+
     const response = await fetch(decodedUrl, {
       headers: {
         'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
@@ -44,12 +53,9 @@ export async function GET(request: Request) {
       return NextResponse.json({ error: 'Failed to fetch key' }, { status: 500 });
     }
 
-    const headers = new Headers();
-    headers.set('Content-Type', response.headers.get('Content-Type') || 'application/octet-stream');
-    headers.set('Access-Control-Allow-Origin', '*');
-    headers.set('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
-    headers.set('Access-Control-Allow-Headers', 'Content-Type, Range, Origin, Accept');
-    headers.set('Access-Control-Expose-Headers', 'Content-Length, Content-Range');
+    const headers = buildProxyStreamHeaders(
+      response.headers.get('Content-Type') || 'application/octet-stream'
+    );
 
     return new Response(response.body, { headers });
   } catch (error) {

src/app/api/proxy/vod/m3u8/route.ts

@@ -4,6 +4,8 @@ import { NextResponse } from "next/server";
 
 import { getConfig } from "@/lib/config";
 import { getBaseUrl, resolveUrl } from "@/lib/live";
+import { validateProxyUrlServerSide } from '@/lib/server/ssrf';
+import { buildProxyM3u8Headers, buildProxyStreamHeaders } from '@/lib/server/proxy-headers';
 
 export const runtime = 'nodejs';
 
@@ -38,6 +40,12 @@ export async function GET(request: Request) {
   try {
     const decodedUrl = decodeURIComponent(url);
 
+    // 安全校验：防 SSRF 拦截请求内网或非法 URL
+    const isSafeUrl = await validateProxyUrlServerSide(decodedUrl);
+    if (!isSafeUrl) {
+      return NextResponse.json({ error: 'Proxy request to local or invalid network is forbidden' }, { status: 403 });
+    }
+
     response = await fetch(decodedUrl, {
       cache: 'no-cache',
       redirect: 'follow',
@@ -66,23 +74,14 @@ export async function GET(request: Request) {
       // 重写 M3U8 内容
       const modifiedContent = rewriteM3U8Content(m3u8Content, baseUrl, request, source);
 
-      const headers = new Headers();
-      headers.set('Content-Type', contentType || 'application/vnd.apple.mpegurl');
-      headers.set('Access-Control-Allow-Origin', '*');
-      headers.set('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
-      headers.set('Access-Control-Allow-Headers', 'Content-Type, Range, Origin, Accept');
-      headers.set('Cache-Control', 'no-cache');
-      headers.set('Access-Control-Expose-Headers', 'Content-Length, Content-Range');
+      const headers = buildProxyM3u8Headers(contentType || undefined);
       return new Response(modifiedContent, { headers });
     }
     // just proxy
-    const headers = new Headers();
-    headers.set('Content-Type', response.headers.get('Content-Type') || 'application/vnd.apple.mpegurl');
-    headers.set('Access-Control-Allow-Origin', '*');
-    headers.set('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
-    headers.set('Access-Control-Allow-Headers', 'Content-Type, Range, Origin, Accept');
+    const headers = buildProxyStreamHeaders(
+      response.headers.get('Content-Type') || 'application/vnd.apple.mpegurl'
+    );
     headers.set('Cache-Control', 'no-cache');
-    headers.set('Access-Control-Expose-Headers', 'Content-Length, Content-Range');
 
     // 直接返回视频流
     return new Response(response.body, {

src/app/api/proxy/vod/segment/route.ts

@@ -1,9 +1,10 @@
 /* eslint-disable no-console,@typescript-eslint/no-explicit-any */
 
-import { NextResponse } from "next/server";
+import { NextResponse } from 'next/server';
 
-import { getConfig } from "@/lib/config";
-import { isValidUrlForProxy } from "@/lib/utils";
+import { getConfig } from '@/lib/config';
+import { validateProxyUrlServerSide } from '@/lib/server/ssrf';
+import { buildProxyStreamHeaders } from '@/lib/server/proxy-headers';
 
 export const runtime = 'nodejs';
 
@@ -44,8 +45,9 @@ export async function GET(request: Request) {
   try {
     const decodedUrl = decodeURIComponent(url);
 
-    // 安全校验：防 SSRF 拦截请求内网或非法 URL
-    if (source === DIRECT_PLAY_SOURCE && !isValidUrlForProxy(decodedUrl)) {
+    // 安全校验：防 SSRF 拦截请求内网或非法 URL (强制检查所有代理请求)
+    const isSafeUrl = await validateProxyUrlServerSide(decodedUrl);
+    if (!isSafeUrl) {
       return NextResponse.json({ error: 'Proxy request to local or invalid network is forbidden' }, { status: 403 });
     }
 
@@ -59,19 +61,14 @@ export async function GET(request: Request) {
       return NextResponse.json({ error: 'Failed to fetch segment' }, { status: 500 });
     }
 
-    const headers = new Headers();
-    headers.set('Content-Type', response.headers.get('Content-Type') || 'video/mp2t');
-    headers.set('Access-Control-Allow-Origin', '*');
-    headers.set('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
-    headers.set('Access-Control-Allow-Headers', 'Content-Type, Range, Origin, Accept');
-    headers.set('Accept-Ranges', 'bytes');
-    headers.set('Access-Control-Expose-Headers', 'Content-Length, Content-Range');
-    const contentLength = response.headers.get('content-length');
-    if (contentLength) {
-      headers.set('Content-Length', contentLength);
-    }
+    const headers = buildProxyStreamHeaders(
+      response.headers.get('Content-Type') || 'video/mp2t',
+      response.headers.get('content-length')
+    );
 
     // 使用流式传输，避免占用内存
+    let isCancelled = false;
+
     const stream = new ReadableStream({
       start(controller) {
         if (!response?.body) {
@@ -80,7 +77,6 @@ export async function GET(request: Request) {
         }
 
         reader = response.body.getReader();
-        const isCancelled = false;
 
         function pump() {
           if (isCancelled || !reader) {
@@ -122,6 +118,7 @@ export async function GET(request: Request) {
         pump();
       },
       cancel() {
+        isCancelled = true;
         // 当流被取消时，确保释放所有资源
         if (reader) {
           try {