Add subscription agents, local repos, and Russian locale

[x0doit]

Summary

• Add Russian locale resources and language toggle coverage.
• Add ChatGPT subscription auth mode for agents, including subscription model choices in the agent UI.
• Expose MCP tools for listing, creating, updating, and deleting agents, their MCP servers, and skills.
• Allow agent project roles to be assigned and updated through the API and agent tools.
• Add a local filesystem repository adapter for sandboxed local development workflows.
• Make local sandbox startup more robust for MCP builds and OpenHands home credentials.

Testing

• apps/web: bun run build; bun run test -- LanguageToggle
• apps/mcp: bun run build; bun run test
• services/ai-agent: python -m compileall -q src tests; pytest tests/test_builder.py tests/test_docker_workspace.py -q
• services/api: go test ./internal/service/agent ./internal/transport/http/handler

[pikann]

Thanks for the awesome PR! 🙌

Could you please fix the CI failures and resolve the conflicts when you have a chance? If you're busy, just let me know—I'd be happy to jump in and help out to get this merged. Thanks again!