remove "transpile-only" in tsconfig, use tsx

[heyitsaamir]

1. Remove nodemon/ts-node deps in favor of tsx. Tsx is much faster than ts-node, but it doesn't do typechecking by default. (We were actually not doing typechecking either because tsconfig was set to transpile-only (which this PR also fixes)).
2. Switches tsconfig to not be transpile only because users and agents should know when types are wrong, so they can fix those errors proactively. Now, npm run build will actually throw if the typescript has errors.

Tested it by creating new apps, and running them. Making sure they pick up the .env files automatically.