v0.9.9: User-based configuration routing for providers, rotations, autoselects, and OAuth2 credentials

- Config admin (from aisbf.json, user_id=None) saves configurations to JSON files
- Database users save configurations to the database (user_providers, user_rotations, user_autoselects tables)
- Dashboard endpoints check user type and route accordingly
- File upload endpoint supports both config admin (files) and database users (database)
- MCP server tools accept user_id parameter and route to appropriate storage
- OAuth2 credential handling already implemented this pattern (Claude, Kilo, Codex)
- Updated CHANGELOG.md, setup.py, and pyproject.toml