refactor(websocket): remove unused broadcastToSession export (#45)

## Removed

- `broadcastToSession` from `server/plugins/websocket.js` — an exported but never-imported, never-called dead-code function. Its dependencies (`getSessionConnections`, `addSessionConnection`, `removeSessionConnection`) are retained since they remain actively used for per-session connection tracking within the plugin.

## Notes

- Full repository search confirms zero remaining references to `broadcastToSession`.
- ESLint passes; full test suite passes (50 files, 406 tests).

Closes #40

---------

Co-authored-by: Madison Grubb <madison@elastiflow.com>
Reviewed-on: #45

server/plugins/websocket.js

@@ -43,16 +43,6 @@ export function removeSessionConnection(sessionId, ws) {
   }
 }
 
-export function broadcastToSession(sessionId, message) {
-  const conns = getSessionConnections(sessionId)
-  const data = JSON.stringify(message)
-  for (const ws of conns) {
-    if (ws.readyState === 1) { // OPEN
-      ws.send(data)
-    }
-  }
-}
-
 export default defineNitroPlugin((nitroApp) => {
   nitroApp.hooks.hook('ready', async () => {
     const server = nitroApp.h3App.server || nitroApp.h3App.nodeServer