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/models/__init__.py

@@ -0,0 +1,20 @@
+from .base import Base
+from .users import User
+from .hosts import Host, ProbeType
+from .monitors import PingResult, DnsResult, PingStatus, DnsStatus
+from .metrics import PluginMetric
+from .alerts import AlertRule, AlertState, AlertEvent, AlertOperator, AlertStateEnum
+from .ansible import AnsibleRun, AnsibleRunStatus
+from .settings import AppSetting
+from .dashboard import Dashboard, DashboardWidget, DashboardShareToken
+
+__all__ = [
+    "Base", "User",
+    "Host", "ProbeType",
+    "PingResult", "DnsResult", "PingStatus", "DnsStatus",
+    "PluginMetric",
+    "AlertRule", "AlertState", "AlertEvent", "AlertOperator", "AlertStateEnum",
+    "AnsibleRun", "AnsibleRunStatus",
+    "AppSetting",
+    "Dashboard", "DashboardWidget", "DashboardShareToken",
+]