fix: correct Grav multi-site setup and rename governance to charters

- Fix setup.php to use Grav's native environment-based multi-site
  - Set GRAV_ENVIRONMENT constant instead of overriding streams
  - Return empty array to let Grav handle stream configuration
- Rename governance.turnsys.com to charters.turnsys.com
  - Update setup.php hostname mapping
  - Update configure-sites.sh site title
  - Update etc-hosts-entries.txt
  - Rename mdbook source directory
  - Rename container environment directory
- Update site title from "TSYS Group Governance" to "TSYS Group Charters"

The stream initialization error was caused by setup.php returning
stream configurations that conflicted with Grav's core streams.
Grav's native environment handling properly manages stream prefixes
when GRAV_ENVIRONMENT is set.

Container is now healthy and responding with 302 redirects.

🤖 Generated with [Crush](https://crush.cbhops.com)

Assisted-by: GLM-5 via Crush <crush@charm.land>

scripts/configure-sites.sh

@@ -2,7 +2,7 @@
 # Generate Grav config and pages for all sites
 
 declare -A SITES=(
-    ["governance.turnsys.com"]="TSYS Group Governance"
+    ["charters.turnsys.com"]="TSYS Group Charters"
     ["plan.afabn.org"]="AFABN Business Plan"
     ["plan.ap4ap.org"]="AP4AP Business Plan"
     ["plan.ezeda.org"]="EzEDA Business Plan"