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/api/stream-discovery.js

@@ -12,7 +12,7 @@ export class StreamDiscoveryAPI {
     discover(request, callbacks) {
         this.close();
 
-        const url = new URL(`${this.baseURL}/api/v1/streams/discover`);
+        const url = new URL(`${this.baseURL}/api/v1/streams/discover`, window.location.origin);
 
         fetch(url, {
             method: 'POST',
@@ -39,7 +39,8 @@ export class StreamDiscoveryAPI {
 
                 for (const line of lines) {
                     if (line.startsWith('event:')) {
-                        const eventType = line.substring(6).trim();
+                        // Parse event type (not currently used, but available for future features)
+                        // const eventType = line.substring(6).trim();
                         continue;
                     }