feat: add local custom networks multisig

[jaime-iobermudez]

Description:

This pull request introduces support for custom Hedera networks by allowing transactions to specify custom consensus nodes. It refactors the transaction schema, DTOs, and service logic to handle both standard and custom networks, and adds migration scripts and utility functions to facilitate this change. The most important changes are grouped below by theme.

Database and Migration Changes:

• Added a migration (1742112000000-AddCustomNetworkSupport.ts) to convert the network column from enum to varchar, and to add a consensus_nodes column for custom network support. The migration handles both upgrade and downgrade scenarios safely.
• Updated transaction.entity.ts to change the network field from an enum to a string and added a nullable consensus_nodes JSONB column.

Application Logic and DTO Updates:

• Extended the Network enum to include CUSTOM, and updated transaction DTOs (create-transaction-request.dto.ts and get-transactions-response.dto.ts) to support consensus node specification for custom networks. [1] [2] [3] [4] [5] [6] [7] [8]
• Updated transaction creation and retrieval logic in transaction.service.ts and autoSubmit.service.ts to use a new buildHederaClient utility, which selects the appropriate network and consensus nodes. [1] [2] [3] [4] [5]

Utility and Configuration Changes:

• Added clientFactory.ts utility to build Hedera clients for both standard and custom networks based on provided consensus nodes.
• Added new TypeORM migration scripts and commands to package.json for easier database management.
• Updated database configuration in app.module.ts to use migrations instead of synchronize, and to automatically run migrations at startup.
• Added example environment variables for multisig and custom consensus node configuration in .env.sample.

Related issue(s):

Fixes #

Notes for reviewer:

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

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