Fix GUI Bugs

[JSv4]

Fixed a couple bugs:

1. Sample frontend .env needs OPENCONTRACTS suffix
2. The navbars were still loading env variables from process.env and not window._env_. Fixed.
3. Sample backend env files had wrong AWS variable names.
4. Added a note on the initial popup that free accounts will have shared extractors

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 70.18%. Comparing base (fb8d946) to head (5fd6382). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #138 +/- ## ======================================= Coverage 70.18% 70.18% ======================================= Files 59 59 Lines 2700 2700 ======================================= Hits 1895 1895 Misses 805 805 ```

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