Ability to reset fee values in dev mode.

Some fee properties (max_cj_fee_abs and max_cj_fee_rel) do not have default values if JM is installed from scratch.
You can now reset those fee values if you want to test what the UI looks like, when a user does not have these values configured.

Misc:

• also added the "dev" badge to the test toggle on the scheduler page

How to test

• Start the app in dev mode with npm run dev:start
• Go to settings -> Click "Adjust fee limits"
• Click the "Reset form values" button (notice how the form becomes invalid)
• Click "Save" - form should not be able to be submitted
• Toggle (disable) "Enable form validation"
• Now click "Save" again - config will be updated
• Visit "Send" or "Sweep" page and verify the alert message saying fee config values are missing

📸

(This message was there all along.. as dev you just never really saw it)