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

src/pwa/pwa-manager.js

@@ -1063,7 +1063,7 @@ class PWAOfflineManager {
 // Singleton pattern
 let instance = null;
 
-const PWAOfflineManager = {
+const PWAOfflineManagerAPI = {
     getInstance() {
         if (!instance) {
             instance = new PWAOfflineManager();
@@ -1078,9 +1078,9 @@ const PWAOfflineManager = {
 
 // Export for module use
 if (typeof module !== 'undefined' && module.exports) {
-    module.exports = PWAOfflineManager;
+    module.exports = PWAOfflineManagerAPI;
 } else if (typeof window !== 'undefined' && !window.PWAOfflineManager) {
-    window.PWAOfflineManager = PWAOfflineManager;
+    window.PWAOfflineManager = PWAOfflineManagerAPI;
 }
 
 // Auto-initialize when DOM is ready
@@ -1088,12 +1088,12 @@ if (typeof window !== 'undefined' && !window.pwaOfflineManager) {
     if (document.readyState === 'loading') {
         document.addEventListener('DOMContentLoaded', () => {
             if (!window.pwaOfflineManager) {
-                window.pwaOfflineManager = PWAOfflineManager.init();
+                window.pwaOfflineManager = PWAOfflineManagerAPI.init();
             }
         });
     } else {
         if (!window.pwaOfflineManager) {
-            window.pwaOfflineManager = PWAOfflineManager.init();
+            window.pwaOfflineManager = PWAOfflineManagerAPI.init();
         }
     }
 }