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/core/alphanumeric-data.js

@@ -0,0 +1,59 @@
+const Mode = require('./mode')
+
+/**
+ * Array of characters available in alphanumeric mode
+ *
+ * As per QR Code specification, to each character
+ * is assigned a value from 0 to 44 which in this case coincides
+ * with the array index
+ *
+ * @type {Array}
+ */
+const ALPHA_NUM_CHARS = [
+  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
+  'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+  ' ', '$', '%', '*', '+', '-', '.', '/', ':'
+]
+
+function AlphanumericData (data) {
+  this.mode = Mode.ALPHANUMERIC
+  this.data = data
+}
+
+AlphanumericData.getBitsLength = function getBitsLength (length) {
+  return 11 * Math.floor(length / 2) + 6 * (length % 2)
+}
+
+AlphanumericData.prototype.getLength = function getLength () {
+  return this.data.length
+}
+
+AlphanumericData.prototype.getBitsLength = function getBitsLength () {
+  return AlphanumericData.getBitsLength(this.data.length)
+}
+
+AlphanumericData.prototype.write = function write (bitBuffer) {
+  let i
+
+  // Input data characters are divided into groups of two characters
+  // and encoded as 11-bit binary codes.
+  for (i = 0; i + 2 <= this.data.length; i += 2) {
+    // The character value of the first character is multiplied by 45
+    let value = ALPHA_NUM_CHARS.indexOf(this.data[i]) * 45
+
+    // The character value of the second digit is added to the product
+    value += ALPHA_NUM_CHARS.indexOf(this.data[i + 1])
+
+    // The sum is then stored as 11-bit binary number
+    bitBuffer.put(value, 11)
+  }
+
+  // If the number of input data characters is not a multiple of two,
+  // the character value of the final character is encoded as a 6-bit binary number.
+  if (this.data.length % 2) {
+    bitBuffer.put(ALPHA_NUM_CHARS.indexOf(this.data[i]), 6)
+  }
+}
+
+module.exports = AlphanumericData