feat(security,ui): self-host React deps, Tailwind, fonts; strict CSP; local QR; better selection state

Replace CDN React/ReactDOM/Babel with local libs; remove Babel and inline scripts
Build Tailwind locally, add safelist; switch to assets/tailwind.css
Self-host Font Awesome and Inter (CSS + woff2); remove external font CDNs
Implement strict CSP (no unsafe-inline/eval; scripts/styles/fonts from self)
Extract inline handlers; move PWA scripts to external files
Add local QR code generation (qrcode lib) and remove api.qrserver.com
Improve SessionTypeSelector visual selection (highlighted background and ring)
Keep PWA working with service worker and offline assets
Refs: CSP hardening, offline-first, no external dependencies

node_modules/pngjs/lib/packer-sync.js

@@ -0,0 +1,56 @@
+"use strict";
+
+let hasSyncZlib = true;
+let zlib = require("zlib");
+if (!zlib.deflateSync) {
+  hasSyncZlib = false;
+}
+let constants = require("./constants");
+let Packer = require("./packer");
+
+module.exports = function (metaData, opt) {
+  if (!hasSyncZlib) {
+    throw new Error(
+      "To use the sync capability of this library in old node versions, please pin pngjs to v2.3.0"
+    );
+  }
+
+  let options = opt || {};
+
+  let packer = new Packer(options);
+
+  let chunks = [];
+
+  // Signature
+  chunks.push(Buffer.from(constants.PNG_SIGNATURE));
+
+  // Header
+  chunks.push(packer.packIHDR(metaData.width, metaData.height));
+
+  if (metaData.gamma) {
+    chunks.push(packer.packGAMA(metaData.gamma));
+  }
+
+  let filteredData = packer.filterData(
+    metaData.data,
+    metaData.width,
+    metaData.height
+  );
+
+  // compress it
+  let compressedData = zlib.deflateSync(
+    filteredData,
+    packer.getDeflateOptions()
+  );
+  filteredData = null;
+
+  if (!compressedData || !compressedData.length) {
+    throw new Error("bad png - invalid compressed data response");
+  }
+  chunks.push(packer.packIDAT(compressedData));
+
+  // End
+  chunks.push(packer.packIEND());
+
+  return Buffer.concat(chunks);
+};