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/path-exists/readme.md

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+# path-exists [![Build Status](https://travis-ci.org/sindresorhus/path-exists.svg?branch=master)](https://travis-ci.org/sindresorhus/path-exists)
+
+> Check if a path exists
+
+NOTE: `fs.existsSync` has been un-deprecated in Node.js since 6.8.0. If you only need to check synchronously, this module is not needed.
+
+While [`fs.exists()`](https://nodejs.org/api/fs.html#fs_fs_exists_path_callback) is being [deprecated](https://github.com/iojs/io.js/issues/103), there's still a genuine use-case of being able to check if a path exists for other purposes than doing IO with it.
+
+Never use this before handling a file though:
+
+> In particular, checking if a file exists before opening it is an anti-pattern that leaves you vulnerable to race conditions: another process may remove the file between the calls to `fs.exists()` and `fs.open()`. Just open the file and handle the error when it's not there.
+
+
+## Install
+
+```
+$ npm install path-exists
+```
+
+
+## Usage
+
+```js
+// foo.js
+const pathExists = require('path-exists');
+
+(async () => {
+	console.log(await pathExists('foo.js'));
+	//=> true
+})();
+```
+
+
+## API
+
+### pathExists(path)
+
+Returns a `Promise<boolean>` of whether the path exists.
+
+### pathExists.sync(path)
+
+Returns a `boolean` of whether the path exists.
+
+
+## Related
+
+- [path-exists-cli](https://github.com/sindresorhus/path-exists-cli) - CLI for this module
+
+
+## License
+
+MIT © [Sindre Sorhus](https://sindresorhus.com)