feat: add variable interpolation support for WebSocket requests (#6064)

* feat: add variable interpolation support for WebSocket requests

- Add WebSocket body interpolation in interpolateVars function
- Interpolate URL, headers, and all messages in request.body.ws array with full variable context
- Refactor sendWsRequest to use main process preparation (removes duplication)
- Add mode property to wsRequest object for proper request type detection
- Ensure consistent variable precedence matching HTTP/gRPC requests
- Centralize all interpolation logic in main process via prepareWsRequest

* Add Playwright tests for WebSocket variable interpolation

- Add tests for URL interpolation (wss://echo.{{url}}.org)
- Add tests for message content interpolation ({"test": "{{data}}"})
- Update test fixtures to use wss://echo.websocket.org echo server
- Add WEBSOCKET_FLOWS.md documentation
- Refactor queueWsMessage to handle variable interpolation in main process

* removed ws flow documentation

* chore: updated the network/index.js file to reduce merge conflicts by moving around code

* fix: added collection and item to WsQueryUrl Editor to fix available variable highlight

* chore: remove unnecessary whitespace in WebSocket event handlers

---------

Co-authored-by: Sid <siddharth@usebruno.com>

tests/websockets/variable-interpolation/init-user-data/preferences.json

@@ -0,0 +1,10 @@
+{
+  "maximized": false,
+  "lastOpenedCollections": [
+    "{{projectRoot}}/tests/websockets/variable-interpolation/fixtures/collection"
+  ],
+  "beta": {
+    "websocket": true
+  }
+}
+