[Code health] Simplify npm scripts

[gino-m]

Align with expectations of developers familiar with npm. For ex:

{
  "scripts": {
    "start": "run-p start:ng emulators",
    "start:ng": "ng serve",
    "emulators": "firebase emulators:start --import=./seed --export-on-exit",
 
    "build:dev": "ng build --configuration development",
    "deploy:dev": "npm run build:dev && firebase deploy -P dev-project-id",
    
    "build:prod": "ng build --configuration production",
    "deploy:prod": "npm run build:prod && firebase deploy -P prod-project-id"
  }
}

For local dev - npm i then npm start.