Restrict orders to enabled networks

[sundayonah]

Description

This PR ensures that payments can only be initiated for networks that are actively supported by introducing an is_enabled field to the network table. This change prevents payments on disabled networks and restricts the system to only fetch and use enabled networks.

Key Changes:

• Added is_enabled field to the network table with a default value of false.
• Updated the Network entity schema to include is_enabled.
• Modified setRPCClients to fetch and use only enabled networks.
• Implemented validation in POST /sender/orders to prevent payments on disabled networks.
• Ensured new networks default to is_enabled = false if not explicitly set.

References

closes #422

Testing

• Test that payments are blocked for disabled networks.
• Test that setRPCClients only fetches and connects to enabled networks.
• Test that the is_enabled field defaults to false for new networks.

Checklist

• I have added documentation and tests for new/changed functionality in this PR
• All active GitHub checks for tests, formatting, and security are passing
• The correct base branch is being used, if not main