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/sync-reader.js

@@ -0,0 +1,45 @@
+"use strict";
+
+let SyncReader = (module.exports = function (buffer) {
+  this._buffer = buffer;
+  this._reads = [];
+});
+
+SyncReader.prototype.read = function (length, callback) {
+  this._reads.push({
+    length: Math.abs(length), // if length < 0 then at most this length
+    allowLess: length < 0,
+    func: callback,
+  });
+};
+
+SyncReader.prototype.process = function () {
+  // as long as there is any data and read requests
+  while (this._reads.length > 0 && this._buffer.length) {
+    let read = this._reads[0];
+
+    if (
+      this._buffer.length &&
+      (this._buffer.length >= read.length || read.allowLess)
+    ) {
+      // ok there is any data so that we can satisfy this request
+      this._reads.shift(); // == read
+
+      let buf = this._buffer;
+
+      this._buffer = buf.slice(read.length);
+
+      read.func.call(this, buf.slice(0, read.length));
+    } else {
+      break;
+    }
+  }
+
+  if (this._reads.length > 0) {
+    return new Error("There are some read requests waitng on finished stream");
+  }
+
+  if (this._buffer.length > 0) {
+    return new Error("unrecognised content at end of stream");
+  }
+};