docs: mirror upstream Code.gs locally (assets/apps_script/)

Two reasons to pin a copy in the repo:

1. Users on networks where raw.githubusercontent.com is intermittent
   can still get the deploy-ready file via a repo ZIP / clone.
2. The Apps Script relay protocol between mhrv-rs and Code.gs is
   informal — upstream changes can silently break us. Keeping a
   snapshot lets future-us diff against what we tested against
   when diagnosing protocol-drift bugs.

Fetched verbatim from:
  https://raw.githubusercontent.com/masterking32/MasterHttpRelayVPN/refs/heads/python_testing/apps_script/Code.gs

Credit stays with @masterking32. The assets/apps_script/README.md
next to it calls out that we don't modify this file — users deploy
it as-is into their own Google Apps Script project.

Updated the Setup Guide link in both the English and Persian
sections so offline / restricted-network users have a fallback path.

assets/apps_script/Code.gs

@@ -0,0 +1,141 @@
+/**
+ * DomainFront Relay — Google Apps Script
+ *
+ * TWO modes:
+ *   1. Single:  POST { k, m, u, h, b, ct, r }       → { s, h, b }
+ *   2. Batch:   POST { k, q: [{m,u,h,b,ct,r}, ...] } → { q: [{s,h,b}, ...] }
+ *      Uses UrlFetchApp.fetchAll() — all URLs fetched IN PARALLEL.
+ *
+ * DEPLOYMENT:
+ *   1. Go to https://script.google.com → New project
+ *   2. Delete the default code, paste THIS entire file
+ *   3. Click Deploy → New deployment
+ *   4. Type: Web app  |  Execute as: Me  |  Who has access: Anyone
+ *   5. Copy the Deployment ID into config.json as "script_id"
+ *
+ * CHANGE THE AUTH KEY BELOW TO YOUR OWN SECRET!
+ */
+
+const AUTH_KEY = "CHANGE_ME_TO_A_STRONG_SECRET";
+
+// Keep browser capability headers (sec-ch-ua*, sec-fetch-*) intact.
+// Some modern apps, notably Google Meet, use them for browser gating.
+const SKIP_HEADERS = {
+  host: 1, connection: 1, "content-length": 1,
+  "transfer-encoding": 1, "proxy-connection": 1, "proxy-authorization": 1,
+  "priority": 1, te: 1,
+};
+
+function doPost(e) {
+  try {
+    var req = JSON.parse(e.postData.contents);
+    if (req.k !== AUTH_KEY) return _json({ e: "unauthorized" });
+
+    // Batch mode: { k, q: [...] }
+    if (Array.isArray(req.q)) return _doBatch(req.q);
+
+    // Single mode
+    return _doSingle(req);
+  } catch (err) {
+    return _json({ e: String(err) });
+  }
+}
+
+function _doSingle(req) {
+  if (!req.u || typeof req.u !== "string" || !req.u.match(/^https?:\/\//i)) {
+    return _json({ e: "bad url" });
+  }
+  var opts = _buildOpts(req);
+  var resp = UrlFetchApp.fetch(req.u, opts);
+  return _json({
+    s: resp.getResponseCode(),
+    h: _respHeaders(resp),
+    b: Utilities.base64Encode(resp.getContent()),
+  });
+}
+
+function _doBatch(items) {
+  var fetchArgs = [];
+  var errorMap = {};
+
+  for (var i = 0; i < items.length; i++) {
+    var item = items[i];
+    if (!item.u || typeof item.u !== "string" || !item.u.match(/^https?:\/\//i)) {
+      errorMap[i] = "bad url";
+      continue;
+    }
+    var opts = _buildOpts(item);
+    opts.url = item.u;
+    fetchArgs.push({ _i: i, _o: opts });
+  }
+
+  // fetchAll() processes all requests in parallel inside Google
+  var responses = [];
+  if (fetchArgs.length > 0) {
+    responses = UrlFetchApp.fetchAll(fetchArgs.map(function(x) { return x._o; }));
+  }
+
+  var results = [];
+  var rIdx = 0;
+  for (var i = 0; i < items.length; i++) {
+    if (errorMap.hasOwnProperty(i)) {
+      results.push({ e: errorMap[i] });
+    } else {
+      var resp = responses[rIdx++];
+      results.push({
+        s: resp.getResponseCode(),
+        h: _respHeaders(resp),
+        b: Utilities.base64Encode(resp.getContent()),
+      });
+    }
+  }
+  return _json({ q: results });
+}
+
+function _buildOpts(req) {
+  var opts = {
+    method: (req.m || "GET").toLowerCase(),
+    muteHttpExceptions: true,
+    followRedirects: req.r !== false,
+    validateHttpsCertificates: true,
+    escaping: false,
+  };
+  if (req.h && typeof req.h === "object") {
+    var headers = {};
+    for (var k in req.h) {
+      if (req.h.hasOwnProperty(k) && !SKIP_HEADERS[k.toLowerCase()]) {
+        headers[k] = req.h[k];
+      }
+    }
+    opts.headers = headers;
+  }
+  if (req.b) {
+    opts.payload = Utilities.base64Decode(req.b);
+    if (req.ct) opts.contentType = req.ct;
+  }
+  return opts;
+}
+
+function _respHeaders(resp) {
+  try {
+    if (typeof resp.getAllHeaders === "function") {
+      return resp.getAllHeaders();
+    }
+  } catch (err) {}
+  return resp.getHeaders();
+}
+
+function doGet(e) {
+  return HtmlService.createHtmlOutput(
+    "<!DOCTYPE html><html><head><title>My App</title></head>" +
+      '<body style="font-family:sans-serif;max-width:600px;margin:40px auto">' +
+      "<h1>Welcome</h1><p>This application is running normally.</p>" +
+      "</body></html>"
+  );
+}
+
+function _json(obj) {
+  return ContentService.createTextOutput(JSON.stringify(obj)).setMimeType(
+    ContentService.MimeType.JSON
+  );
+}