feat: Add sandbox integration for MCP

[d42me]

Closes ENG-2426

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Note

Introduces sandbox management to the MCP server and minor client enhancement.

• Adds prime-sandboxes>=0.2.8 dependency and workspace source; exports sandboxes in __init__ and bumps version to 0.1.3
• New prime_mcp/tools/sandboxes.py implementing sandbox operations via AsyncSandboxClient/AsyncTemplateClient
• Extends MCP tools in mcp.py for sandboxes: create_sandbox, list_sandboxes, get_sandbox, delete_sandbox, bulk_delete_sandboxes, get_sandbox_logs, execute_sandbox_command, expose_sandbox_port, unexpose_sandbox_port, list_sandbox_exposed_ports, list_registry_credentials, check_docker_image
• HTTP client: allow JSON payloads on DELETE (client.py, core/client.py)
• Tests: new tests/test_sandbox_tools.py; updates to pod tests to include data_center_id in validations
• Lockfile updated (uv.lock)

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