updating a compose file over the API now saves it, not just deploys it

src/lib/server/stack-paths.ts

@@ -0,0 +1,15 @@
+/**
+ * The ONE formula for a stack's folder under a base dir on a host: `<base>/<stack>`.
+ * Deploy staging (write) and backup (read) share it so they can't diverge (#1383 / #1240).
+ * Pure + dependency-free, so both sides can import it.
+ */
+
+/** Trim + drop trailing slashes: `/data/stacks/` -> `/data/stacks`. */
+export function normalizeBaseDir(base: string): string {
+	return base.trim().replace(/\/+$/, '');
+}
+
+/** `<normalized base>/<stackName>`. Name is used verbatim - do NOT slugify (both sides use it raw). */
+export function stackDirIn(base: string, stackName: string): string {
+	return `${normalizeBaseDir(base)}/${stackName}`;
+}