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/version.js

@@ -0,0 +1,163 @@
+const Utils = require('./utils')
+const ECCode = require('./error-correction-code')
+const ECLevel = require('./error-correction-level')
+const Mode = require('./mode')
+const VersionCheck = require('./version-check')
+
+// Generator polynomial used to encode version information
+const G18 = (1 << 12) | (1 << 11) | (1 << 10) | (1 << 9) | (1 << 8) | (1 << 5) | (1 << 2) | (1 << 0)
+const G18_BCH = Utils.getBCHDigit(G18)
+
+function getBestVersionForDataLength (mode, length, errorCorrectionLevel) {
+  for (let currentVersion = 1; currentVersion <= 40; currentVersion++) {
+    if (length <= exports.getCapacity(currentVersion, errorCorrectionLevel, mode)) {
+      return currentVersion
+    }
+  }
+
+  return undefined
+}
+
+function getReservedBitsCount (mode, version) {
+  // Character count indicator + mode indicator bits
+  return Mode.getCharCountIndicator(mode, version) + 4
+}
+
+function getTotalBitsFromDataArray (segments, version) {
+  let totalBits = 0
+
+  segments.forEach(function (data) {
+    const reservedBits = getReservedBitsCount(data.mode, version)
+    totalBits += reservedBits + data.getBitsLength()
+  })
+
+  return totalBits
+}
+
+function getBestVersionForMixedData (segments, errorCorrectionLevel) {
+  for (let currentVersion = 1; currentVersion <= 40; currentVersion++) {
+    const length = getTotalBitsFromDataArray(segments, currentVersion)
+    if (length <= exports.getCapacity(currentVersion, errorCorrectionLevel, Mode.MIXED)) {
+      return currentVersion
+    }
+  }
+
+  return undefined
+}
+
+/**
+ * Returns version number from a value.
+ * If value is not a valid version, returns defaultValue
+ *
+ * @param  {Number|String} value        QR Code version
+ * @param  {Number}        defaultValue Fallback value
+ * @return {Number}                     QR Code version number
+ */
+exports.from = function from (value, defaultValue) {
+  if (VersionCheck.isValid(value)) {
+    return parseInt(value, 10)
+  }
+
+  return defaultValue
+}
+
+/**
+ * Returns how much data can be stored with the specified QR code version
+ * and error correction level
+ *
+ * @param  {Number} version              QR Code version (1-40)
+ * @param  {Number} errorCorrectionLevel Error correction level
+ * @param  {Mode}   mode                 Data mode
+ * @return {Number}                      Quantity of storable data
+ */
+exports.getCapacity = function getCapacity (version, errorCorrectionLevel, mode) {
+  if (!VersionCheck.isValid(version)) {
+    throw new Error('Invalid QR Code version')
+  }
+
+  // Use Byte mode as default
+  if (typeof mode === 'undefined') mode = Mode.BYTE
+
+  // Total codewords for this QR code version (Data + Error correction)
+  const totalCodewords = Utils.getSymbolTotalCodewords(version)
+
+  // Total number of error correction codewords
+  const ecTotalCodewords = ECCode.getTotalCodewordsCount(version, errorCorrectionLevel)
+
+  // Total number of data codewords
+  const dataTotalCodewordsBits = (totalCodewords - ecTotalCodewords) * 8
+
+  if (mode === Mode.MIXED) return dataTotalCodewordsBits
+
+  const usableBits = dataTotalCodewordsBits - getReservedBitsCount(mode, version)
+
+  // Return max number of storable codewords
+  switch (mode) {
+    case Mode.NUMERIC:
+      return Math.floor((usableBits / 10) * 3)
+
+    case Mode.ALPHANUMERIC:
+      return Math.floor((usableBits / 11) * 2)
+
+    case Mode.KANJI:
+      return Math.floor(usableBits / 13)
+
+    case Mode.BYTE:
+    default:
+      return Math.floor(usableBits / 8)
+  }
+}
+
+/**
+ * Returns the minimum version needed to contain the amount of data
+ *
+ * @param  {Segment} data                    Segment of data
+ * @param  {Number} [errorCorrectionLevel=H] Error correction level
+ * @param  {Mode} mode                       Data mode
+ * @return {Number}                          QR Code version
+ */
+exports.getBestVersionForData = function getBestVersionForData (data, errorCorrectionLevel) {
+  let seg
+
+  const ecl = ECLevel.from(errorCorrectionLevel, ECLevel.M)
+
+  if (Array.isArray(data)) {
+    if (data.length > 1) {
+      return getBestVersionForMixedData(data, ecl)
+    }
+
+    if (data.length === 0) {
+      return 1
+    }
+
+    seg = data[0]
+  } else {
+    seg = data
+  }
+
+  return getBestVersionForDataLength(seg.mode, seg.getLength(), ecl)
+}
+
+/**
+ * Returns version information with relative error correction bits
+ *
+ * The version information is included in QR Code symbols of version 7 or larger.
+ * It consists of an 18-bit sequence containing 6 data bits,
+ * with 12 error correction bits calculated using the (18, 6) Golay code.
+ *
+ * @param  {Number} version QR Code version
+ * @return {Number}         Encoded version info bits
+ */
+exports.getEncodedBits = function getEncodedBits (version) {
+  if (!VersionCheck.isValid(version) || version < 7) {
+    throw new Error('Invalid QR Code version')
+  }
+
+  let d = version << 12
+
+  while (Utils.getBCHDigit(d) - G18_BCH >= 0) {
+    d ^= (G18 << (Utils.getBCHDigit(d) - G18_BCH))
+  }
+
+  return (version << 12) | d
+}