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>

docs/architecture.md

@@ -1,12 +1,12 @@
 # Architecture
 
-Roundtable is a single Quart (async Python) process. There are no separate worker processes, no message brokers, and no build pipeline for the frontend. All monitoring, scheduling, and request handling runs on a single asyncio event loop.
+Steward is a single Quart (async Python) process. There are no separate worker processes, no message brokers, and no build pipeline for the frontend. All monitoring, scheduling, and request handling runs on a single asyncio event loop.
 
 ---
 
 ## Startup Sequence
 
-`create_app()` in `roundtable/app.py` runs these steps synchronously before the event loop starts:
+`create_app()` in `steward/app.py` runs these steps synchronously before the event loop starts:
 
 | Step | What happens |
 |---|---|
@@ -32,14 +32,14 @@ All routes are Quart Blueprints registered in `app.py`:
 
 | Prefix | Blueprint | Module |
 |---|---|---|
-| `/auth/` | `auth_bp` | `roundtable/auth/routes.py` |
-| `/` | `dashboard_bp` | `roundtable/dashboard/routes.py` |
-| `/hosts/` | `hosts_bp` | `roundtable/hosts/routes.py` |
-| `/ping/` | `ping_bp` | `roundtable/ping/routes.py` |
-| `/dns/` | `dns_bp` | `roundtable/dns/routes.py` |
-| `/alerts/` | `alerts_bp` | `roundtable/alerts/routes.py` |
-| `/ansible/` | `ansible_bp` | `roundtable/ansible/routes.py` |
-| `/settings/` | `settings_bp` | `roundtable/settings/routes.py` |
+| `/auth/` | `auth_bp` | `steward/auth/routes.py` |
+| `/` | `dashboard_bp` | `steward/dashboard/routes.py` |
+| `/hosts/` | `hosts_bp` | `steward/hosts/routes.py` |
+| `/ping/` | `ping_bp` | `steward/ping/routes.py` |
+| `/dns/` | `dns_bp` | `steward/dns/routes.py` |
+| `/alerts/` | `alerts_bp` | `steward/alerts/routes.py` |
+| `/ansible/` | `ansible_bp` | `steward/ansible/routes.py` |
+| `/settings/` | `settings_bp` | `steward/settings/routes.py` |
 | `/plugins/<name>/` | plugin blueprint | `plugins/<name>/routes.py` |
 
 Plugin blueprints are mounted automatically by `load_plugins()` using the plugin directory name as the URL prefix.
@@ -48,7 +48,7 @@ Plugin blueprints are mounted automatically by `load_plugins()` using the plugin
 
 ## Scheduler
 
-`roundtable/core/scheduler.py` exports two things:
+`steward/core/scheduler.py` exports two things:
 
 - `ScheduledTask` dataclass — holds a `name`, `coro_factory` (zero-argument callable returning a coroutine), `interval_seconds`, and optional `run_on_startup` flag
 - `start_scheduler(tasks)` — async function that loops every second, calling `asyncio.create_task()` for each task whose interval has elapsed
@@ -93,9 +93,9 @@ This means the only file you must touch to get the app running is the database U
 
 No JavaScript framework, no build step. The frontend is:
 
-- **Jinja2 templates** rendered server-side (`roundtable/templates/`)
+- **Jinja2 templates** rendered server-side (`steward/templates/`)
 - **HTMX** for live-updating fragments (dashboard widgets, ping pills, DNS status)
-- A single CSS design system in `roundtable/templates/base.html` using CSS custom properties
+- A single CSS design system in `steward/templates/base.html` using CSS custom properties
 
 Live-updating widgets use HTMX polling:
 ```html