fix(cleanup): resolve 9 low-priority issues (P34-P42)

P34: Remove test_sample plugin from production code
P35: Remove CompanyContact=None dead code from contact.py
P36: Change Plugin.config from Text to JSONB (model + migration 0117 + service)
P37: Add AI comment about workspace overengineering in workspace.py
P38: Add container resource limits to docker-compose.yaml
P39: Guest TTL 1800 not found — already migrated to regular users
P40: Add AI comment about missing IP/Device binding in session.py
P41: Fix Redis healthcheck to use auth password
P42: RLS migration history comment already present in alembic/env.py

app/services/plugin_service.py

@@ -205,17 +205,12 @@ class PluginService:
     async def get_plugin_config(self, db: AsyncSession, name: str) -> dict[str, Any]:
         """Get the configuration for a plugin.
 
-        Returns the plugin's config field parsed from JSON string.
+        Returns the plugin's config field (JSONB, already parsed by SQLAlchemy).
         """
         record = await self._registry._get_plugin_record(db, name)
         if record is None:
             raise ValueError(f"Plugin '{name}' is not installed")
-        import json
-        config_str = getattr(record, "config", None) or "{}"
-        try:
-            return json.loads(config_str) if isinstance(config_str, str) else config_str or {}
-        except (json.JSONDecodeError, TypeError):
-            return {}
+        return getattr(record, "config", None) or {}
 
     async def update_plugin_config(
         self,
@@ -227,15 +222,13 @@ class PluginService:
     ) -> dict[str, Any]:
         """Update the configuration for a plugin.
 
-        Stores the config as a JSON string in the plugin's config field.
+        Stores the config directly as JSONB in the plugin's config field.
         """
-        import json
-
         record = await self._registry._get_plugin_record(db, name)
         if record is None:
             raise ValueError(f"Plugin '{name}' is not installed")
 
-        record.config = json.dumps(config)
+        record.config = config
         await db.flush()
 
         if tenant_id and user_id: