Fix SSE stream discovery and add ESLint for WebUI

JavaScript fixes:
- Fix Invalid URL error in stream-discovery.js by adding window.location.origin as base URL
- Fix SSE race condition: ensure all stream_found events sent before complete event
- Comment unused eventType variable in stream-discovery.js
- Comment unused FrigateGenerator import in config-panel.js
- Fix quote style (double to single quotes)

Go fixes:
- Add sync.WaitGroup for result collector to prevent premature SSE closure
- Add logging for stream_found events
- Fix ERR_INCOMPLETE_CHUNKED_ENCODING by waiting for all streams to be sent

ESLint setup:
- Add ESLint v8.57.1 with .eslintrc.cjs config for ES2022 modules
- Add npm scripts for lint and lint:fix
- Update .gitignore for node_modules and package-lock.json

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

webui/web/js/ui/config-panel.js

@@ -1,5 +1,5 @@
 import { Go2RTCGenerator } from '../config-generators/go2rtc/index.js';
-import { FrigateGenerator } from '../config-generators/frigate/index.js';
+// import { FrigateGenerator } from '../config-generators/frigate/index.js'; // Reserved for future use
 
 export class ConfigPanel {
     constructor() {