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/qrcode/lib/renderer/png.js

@@ -0,0 +1,78 @@
+const fs = require('fs')
+const PNG = require('pngjs').PNG
+const Utils = require('./utils')
+
+exports.render = function render (qrData, options) {
+  const opts = Utils.getOptions(options)
+  const pngOpts = opts.rendererOpts
+  const size = Utils.getImageWidth(qrData.modules.size, opts)
+
+  pngOpts.width = size
+  pngOpts.height = size
+
+  const pngImage = new PNG(pngOpts)
+  Utils.qrToImageData(pngImage.data, qrData, opts)
+
+  return pngImage
+}
+
+exports.renderToDataURL = function renderToDataURL (qrData, options, cb) {
+  if (typeof cb === 'undefined') {
+    cb = options
+    options = undefined
+  }
+
+  exports.renderToBuffer(qrData, options, function (err, output) {
+    if (err) cb(err)
+    let url = 'data:image/png;base64,'
+    url += output.toString('base64')
+    cb(null, url)
+  })
+}
+
+exports.renderToBuffer = function renderToBuffer (qrData, options, cb) {
+  if (typeof cb === 'undefined') {
+    cb = options
+    options = undefined
+  }
+
+  const png = exports.render(qrData, options)
+  const buffer = []
+
+  png.on('error', cb)
+
+  png.on('data', function (data) {
+    buffer.push(data)
+  })
+
+  png.on('end', function () {
+    cb(null, Buffer.concat(buffer))
+  })
+
+  png.pack()
+}
+
+exports.renderToFile = function renderToFile (path, qrData, options, cb) {
+  if (typeof cb === 'undefined') {
+    cb = options
+    options = undefined
+  }
+
+  let called = false
+  const done = (...args) => {
+    if (called) return
+    called = true
+    cb.apply(null, args)
+  }
+  const stream = fs.createWriteStream(path)
+
+  stream.on('error', done)
+  stream.on('close', done)
+
+  exports.renderToFileStream(stream, qrData, options)
+}
+
+exports.renderToFileStream = function renderToFileStream (stream, qrData, options) {
+  const png = exports.render(qrData, options)
+  png.pack().pipe(stream)
+}