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/templates/settings/_install_result.html

@@ -0,0 +1,20 @@
+{# settings/_install_result.html — inline result after install/reload action #}
+<div id="catalog-result-{{ name }}"
+     style="margin-top:0.6rem;padding:0.5rem 0.75rem;border-radius:5px;font-size:0.82rem;
+            background:{% if success %}var(--green-dim){% else %}var(--red-dim){% endif %};
+            color:{% if success %}var(--green){% else %}#ff8090{% endif %};">
+  {{ message }}
+  {% if restart_required %}
+  &nbsp;·&nbsp;
+  <form method="post" action="/settings/plugins/restart/"
+        hx-post="/settings/plugins/restart/"
+        hx-target="#restart-banner"
+        hx-swap="outerHTML"
+        style="display:inline;margin:0;">
+    <button type="submit"
+            style="background:none;border:none;padding:0;color:var(--yellow);cursor:pointer;font-size:0.82rem;text-decoration:underline;">
+      Restart now
+    </button>
+  </form>
+  {% endif %}
+</div>