Propose migrating from manual os.getenv() calls to dynaconf for
file-based configuration. Key decisions: envvar_prefix=False for
backward compatibility, MCP_DEPLOYMENT_MODE as environment switcher,
TOML settings files with secret separation, and incremental migration
via adapter pattern.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
