Remove unmaintained localnet infrastructure and documentation

[Copilot]

This PR removes the unmaintained localnet infrastructure that has been causing issues for bug bounty hunters and developers. The localnet setup was problematic because it gave users false confidence in bugs that don't actually work in production environments.

What's removed

Core localnet files:

• docker-compose.yml - The main Docker Compose configuration for the 4-node localnet
• networks/local/ directory - Complete localnet infrastructure including:
  • Docker build configuration and Makefile
  • localnode Docker image definition and scripts
  • Configuration templates

Build targets:

• localnet-start - Command to start the 4-node localnet
• localnet-stop - Command to stop the localnet
• build-docker-localnode - Command to build the localnode Docker image

Documentation:

• docs/networks/docker-compose.md - Complete localnet setup guide
• References to localnet in DOCKER/README.md and other docs

What's preserved

This removal is surgical and targeted:

• E2E testing infrastructure remains intact - Uses separate docker-compose functionality
• Core build and test workflows unchanged - All make build, make test commands work
• Contract testing hooks preserved - Though currently non-functional due to upstream dredd issues
• All other Docker usage unaffected - Including Ivy proofs and other tooling

Impact

• Eliminates confusion for bug bounty hunters who were relying on non-production localnet
• Reduces maintenance burden by removing unmaintained code paths
• Cleaner repository with 300+ lines of obsolete configuration removed
• No functional regression - localnet was already problematic and not used in CI

The contract testing functionality (which depended on localnet) has been updated to clearly indicate it's currently unavailable, providing better clarity for developers working on RPC changes.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Remove the unmaintained local net</issue_title>
<issue_description>we don't maintain or use the local net script here, which is problematic as many people trying to claim bug bounties use it and get false confidence in bugs that don't actually do anything.

therefore we should remove it</issue_description>

<agent_instructions>remove the local net script and documentation relevant to it</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Remove the unmaintained local net #2597

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