Admin Panel/Settings/Layout, for PWA: Custom head meta, link, icons, assetlinks.json, site.webmanifest.

Thanks to xet7 !

server/routes/customHeadAssets.js

@@ -0,0 +1,81 @@
+import { WebApp } from 'meteor/webapp';
+import { Meteor } from 'meteor/meteor';
+import fs from 'fs';
+import path from 'path';
+import Settings from '/models/settings';
+
+const shouldServeContent = (value) =>
+  typeof value === 'string' && value.trim().length > 0;
+
+const getDefaultFileContent = (filename) => {
+  try {
+    const filePath = path.join(Meteor.absolutePath, 'public', filename);
+    if (fs.existsSync(filePath)) {
+      return fs.readFileSync(filePath, 'utf-8');
+    }
+  } catch (e) {
+    console.error(`Error reading default file ${filename}:`, e);
+  }
+  return null;
+};
+
+const respondWithText = (res, contentType, body) => {
+  res.writeHead(200, {
+    'Content-Type': `${contentType}; charset=utf-8`,
+    'Access-Control-Allow-Origin': '*',
+  });
+  res.end(body);
+};
+
+WebApp.connectHandlers.use('/site.webmanifest', (req, res, next) => {
+  if (req.method !== 'GET' && req.method !== 'HEAD') return next();
+  const setting = Settings.findOne(
+    {},
+    {
+      fields: {
+        customHeadEnabled: 1,
+        customManifestEnabled: 1,
+        customManifestContent: 1,
+      },
+    },
+  );
+
+  // Serve custom content if enabled
+  if (setting && setting.customHeadEnabled && setting.customManifestEnabled && shouldServeContent(setting.customManifestContent)) {
+    return respondWithText(res, 'application/manifest+json', setting.customManifestContent);
+  }
+
+  // Fallback to default manifest file
+  const defaultContent = getDefaultFileContent('site.webmanifest.default');
+  if (defaultContent) {
+    return respondWithText(res, 'application/manifest+json', defaultContent);
+  }
+
+  return next();
+});
+
+WebApp.connectHandlers.use('/.well-known/assetlinks.json', (req, res, next) => {
+  if (req.method !== 'GET' && req.method !== 'HEAD') return next();
+  const setting = Settings.findOne(
+    {},
+    {
+      fields: {
+        customAssetLinksEnabled: 1,
+        customAssetLinksContent: 1,
+      },
+    },
+  );
+
+  // Serve custom content if enabled
+  if (setting && setting.customAssetLinksEnabled && shouldServeContent(setting.customAssetLinksContent)) {
+    return respondWithText(res, 'application/json', setting.customAssetLinksContent);
+  }
+
+  // Fallback to default assetlinks file
+  const defaultContent = getDefaultFileContent('.well-known/assetlinks.json.default');
+  if (defaultContent) {
+    return respondWithText(res, 'application/json', defaultContent);
+  }
+
+  return next();
+});