feat: add self-hosted mem0 MCP bridge

[vabs95]

This PR adds a self-hosted Mem0 path for coding-agent integrations. It updates the mem0-plugin hook scripts to support a self-hosted REST API mode via environment variables, so
lifecycle hooks can store and retrieve memories from a VPS-hosted Mem0 instance instead of Mem0 Cloud.

It also adds a self-hosted MCP bridge service that exposes the familiar memory tools over Streamable HTTP and forwards them to the local Mem0 REST server. This gives Codex, Claude
Code, and other MCP-capable tools a stable memory tool surface while keeping all data on the self-hosted backend.

In addition, the PR adds an automated upstream sync workflow that opens a PR from mem0ai/mem0@main into the fork and enables auto-merge once checks pass.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactor (no functional changes)
• Documentation update

Breaking Changes

N/A

Test Coverage

• I added/updated unit tests
• I added/updated integration tests
• I tested manually (describe below)
• No tests needed (explain why)

Manual checks:

• pytest integrations/mem0-plugin/tests/test_self_hosted_api.py integrations/mem0-plugin/tests/test_search.py integrations/mem0-plugin/tests/test_write_path.py tests/
  test_mem0_mcp_bridge.py

• docker compose -f docker-compose.yml config

• python -c "import mem0_mcp_bridge.server" with PYTHONPATH=server/mcp

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have added tests that prove my fix/feature works
• New and existing tests pass locally
• I have updated documentation if needed