feat(migration): migrate legacy owner data and update config reference handling

- Implemented a migration process to move resources from the legacy owner "default" to the new default owner "local", ensuring no data loss during the transition.
- Updated configuration reference handling to replace legacy `$VAR_`, `$SECRET_`, and `$CONTEXT_` prefixes with mustache-style `{{ vars.name }}`, `{{ secrets.name }}`, and `{{ context.name }}`.
- Enhanced YAML configuration files and scripts to reflect the new mustache syntax, improving consistency across the application.
- Added tests to validate the migration process and ensure proper handling of legacy references.
- Updated documentation to guide users on the new configuration reference format.

packages/web/src/components/VariableEditorModal.jsx

@@ -129,7 +129,9 @@ export function VariableEditorModal({ mode, initial, onClose, onSaved }) {
           </label>
           <p className="text-xs opacity-60">
             Stored in plaintext. Use Secrets for credentials. In workflows use{" "}
-            <span className="font-mono">$VAR_name</span> as a whole field.
+            <span className="font-mono">{"{{ vars.name }}"}</span> (quote strings that
+            start with <span className="font-mono">{"{"}</span>). Nested:{" "}
+            <span className="font-mono">{"{{ context.user.id }}"}</span>.
           </p>
           {formError ? <p className="text-error text-sm">{formError}</p> : null}
           {upsert.isError ? (