remove watch.sh dependency from watch task

Task can handle running tasks in parallel, so use that instead of relying on the `watch.sh` script which has shown to be incompatible with Task's interrupt signaling.

also update `watch` task's description.

Taskfile.yml

@@ -66,9 +66,9 @@ tasks:
  - DEV=1 ./node_modules/.bin/nodemon --watch '**/*' -e html,yml,go,js --signal SIGTERM --exec 'go run . --config config.yml'
 
  watch:
- desc: Starts both frontend and backend (with ./watch.sh)
+ desc: Starts both frontend and backend, watching for changes
  cmds:
- - bash ./watch.sh task
+ - task -p watch_frontend watch_backend
 
  clean:
  desc: Clean up build artifacts