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>

docker-compose.yml

@@ -1,8 +1,8 @@
 services:
-  roundtable:
+  steward:
     build: .
-    container_name: roundtable
-    image: roundtable:latest
+    container_name: steward
+    image: steward:latest
     ports:
       - "5000:5000"
     volumes:
@@ -11,7 +11,7 @@ services:
       - /mnt/Data/traefik/log:/var/log/traefik:ro
       - /var/run/docker.sock:/var/run/docker.sock:ro
     environment:
-      - ROUNDTABLE_DATABASE_URL=postgresql+asyncpg://fabledscryer:fabledscryer@db/fabledscryer
+      - STEWARD_DATABASE_URL=postgresql+asyncpg://steward:steward@db/steward
     depends_on:
       db:
         condition: service_healthy
@@ -20,13 +20,13 @@ services:
   db:
     image: postgres:16-alpine
     environment:
-      POSTGRES_USER: fabledscryer
-      POSTGRES_PASSWORD: fabledscryer
-      POSTGRES_DB: fabledscryer
+      POSTGRES_USER: steward
+      POSTGRES_PASSWORD: steward
+      POSTGRES_DB: steward
     volumes:
       - pgdata:/var/lib/postgresql/data
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U fabledscryer"]
+      test: ["CMD-SHELL", "pg_isready -U steward"]
       interval: 5s
       timeout: 5s
       retries: 5