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/core/ansible.md

@@ -1,6 +1,6 @@
 # Ansible Integration
 
-Roundtable can browse, trigger, and stream output from Ansible playbooks directly from the web UI. Runs execute as asyncio tasks inside the same process — no Celery, no external workers.
+Steward can browse, trigger, and stream output from Ansible playbooks directly from the web UI. Runs execute as asyncio tasks inside the same process — no Celery, no external workers.
 
 ---
 
@@ -115,7 +115,7 @@ Output stored in the DB is capped at 1 MB. If truncated, `[output truncated]` is
 
 ## Data Model
 
-`ansible_runs` table (defined in `roundtable/models/ansible.py`):
+`ansible_runs` table (defined in `steward/models/ansible.py`):
 
 | Column | Type | Description |
 |---|---|---|
@@ -137,7 +137,7 @@ Runs older than `data.retention_days` (default 90) are pruned by the `data_clean
 
 | File | Purpose |
 |---|---|
-| `roundtable/ansible/sources.py` | Source discovery, git pull logic |
-| `roundtable/ansible/executor.py` | Subprocess execution and output streaming |
-| `roundtable/ansible/routes.py` | HTTP routes (browse, trigger, stream, history) |
-| `roundtable/models/ansible.py` | `AnsibleRun` model |
+| `steward/ansible/sources.py` | Source discovery, git pull logic |
+| `steward/ansible/executor.py` | Subprocess execution and output streaming |
+| `steward/ansible/routes.py` | HTTP routes (browse, trigger, stream, history) |
+| `steward/models/ansible.py` | `AnsibleRun` model |