chore: rename project Roundtable → Steward

Renames the Python package directory, CLI command, env var prefix,
docker-compose service/container/image, Postgres role/db, and all
visible branding. Marketing form is "Fabled Steward".

Clean break from the previous rebrand: drops the fabledscryer→roundtable
import shim in __init__.py and the FABLEDSCRYER_* env var fallback in
config.py and migrations/env.py. Env vars are now STEWARD_* only.

Heads-up for existing deployments:
- Postgres user/db renamed fabledscryer → steward in docker-compose.yml.
  Existing volumes need the role/db renamed inside Postgres, or override
  POSTGRES_USER/POSTGRES_DB to keep the old names.
- Host-agent systemd unit is now steward-agent.service. Existing agents
  keep running under the old name; reinstall to switch.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

steward/migrations/env.py

@@ -0,0 +1,69 @@
+import asyncio
+from logging.config import fileConfig
+from sqlalchemy import pool
+from sqlalchemy.engine import Connection
+from sqlalchemy.ext.asyncio import async_engine_from_config
+from alembic import context
+from steward.models.base import Base
+import steward.models  # noqa: F401 — registers all models in metadata
+
+config = context.config
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+target_metadata = Base.metadata
+
+
+def get_url() -> str:
+    import os, yaml
+
+    def _env(suffix: str) -> str | None:
+        return os.environ.get(f"STEWARD_{suffix}")
+
+    cfg_path = _env("CONFIG") or "config.yaml"
+    try:
+        with open(cfg_path) as f:
+            cfg = yaml.safe_load(f) or {}
+        url = cfg.get("database", {}).get("url", "")
+    except FileNotFoundError:
+        url = ""
+    return _env("DATABASE_URL") or _env("DATABASE__URL") or url
+
+
+def _resolved_url() -> str:
+    """Return URL from migration_runner config if set, else fall back to get_url()."""
+    return config.get_main_option("sqlalchemy.url") or get_url()
+
+
+def run_migrations_offline() -> None:
+    context.configure(
+        url=_resolved_url(), target_metadata=target_metadata,
+        literal_binds=True, dialect_opts={"paramstyle": "named"},
+    )
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def do_run_migrations(connection: Connection) -> None:
+    context.configure(connection=connection, target_metadata=target_metadata)
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations() -> None:
+    cfg = config.get_section(config.config_ini_section, {})
+    cfg["sqlalchemy.url"] = _resolved_url()
+    connectable = async_engine_from_config(cfg, prefix="sqlalchemy.", poolclass=pool.NullPool)
+    async with connectable.connect() as connection:
+        await connection.run_sync(do_run_migrations)
+    await connectable.dispose()
+
+
+def run_migrations_online() -> None:
+    asyncio.run(run_async_migrations())
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()