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/string-width/index.d.ts

@@ -0,0 +1,29 @@
+declare const stringWidth: {
+	/**
+	Get the visual width of a string - the number of columns required to display it.
+
+	Some Unicode characters are [fullwidth](https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms) and use double the normal width. [ANSI escape codes](https://en.wikipedia.org/wiki/ANSI_escape_code) are stripped and doesn't affect the width.
+
+	@example
+	```
+	import stringWidth = require('string-width');
+
+	stringWidth('a');
+	//=> 1
+
+	stringWidth('古');
+	//=> 2
+
+	stringWidth('\u001B[1m古\u001B[22m');
+	//=> 2
+	```
+	*/
+	(string: string): number;
+
+	// TODO: remove this in the next major version, refactor the whole definition to:
+	// declare function stringWidth(string: string): number;
+	// export = stringWidth;
+	default: typeof stringWidth;
+}
+
+export = stringWidth;