refactor: convert to monorepo with all 21 sites merged

- Merged 21 repos using git subtree (preserves full history)
- Content now at content/{fqdn}/pages/
- Updated setup.php to use user/data/content/ path for Git Sync
- Simplified docker-compose.yml for local testing

Sites included (238 total pages):
- charters.turnsys.com (199 pages)
- plan.knownelement.com (7 pages)
- plan.startinglineproductions.com (10 pages)
- plan.suborbital-systems.com (2 pages)
- 17 other plan.* sites (1 page each)

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

setup.php

@@ -35,10 +35,10 @@ $hostMap = [
 ];
 
 $environment = isset($hostMap[$hostname]) ? $hostMap[$hostname] : 'staticsites.turnsys.com';
-$envPath = GRAV_ROOT . '/user/env/' . $environment;
+$envPath = GRAV_ROOT . '/user/data/content/' . $environment;
 
 if (!is_dir($envPath)) {
-    $envPath = GRAV_ROOT . '/user/env/staticsites.turnsys.com';
+    $envPath = GRAV_ROOT . '/user/data/content/staticsites.turnsys.com';
 }
 
 // Only override page stream - use environment pages, fallback to default