double handling of dollar signs in variables in .env file

[UpcraftLP]

if you use an .env file to specify config variables, and those variables happen to contain dollar signs $, then rover applies two different mechanisms for interpolating those variables:

• first the dotenvy crate tries to interpolate values while loading (this appears to only be documented in the upstream dotenv crate (also see dotenvy silently fails to parse strings with dollar signs allan2/dotenvy#93)
• and then a second time using rover's own variable substitution.

So variables must be escaped TWICE, in different ways: first the value must be enclosed in single quotes, and then each dollar sign needs to be doubled:
MY_ENV_VAR='some$$api$$key'

Ideally, only one of those mechanisms would apply, and be documented which.

Rover Info:
Version: 0.36.2
Install Location: %HOMEPATH%\.rover\bin\rover.exe
OS: Windows 10.0.26100 (Windows 11 Enterprise) [64-bit]
Shell: Powershell 7.5.3