umami: read the admin password from its mounted secret file

The whole-mesh dry-run found umami's runtime crash-looping "admin password is
not set": its `admin` own-secret is mounted at /run/secrets/admin, but the
client read the bare env UMAMI_ADMIN_PASSWORD, which nothing sets. Same shape as
the six tool-runtime credential fixes — read the mounted file first
(MESH_UMAMI_ADMIN_PASSWORD_FILE), falling back to the env. (photos and mailu
remain deeper conversion jobs — a stub app image and a full Mailu config env —
not credential-wiring, tracked separately.)

Claude-Session: https://claude.ai/code/session_01LrgweAeERJYBg88c5cKDzF

modules/umami/client.ts

@@ -2,6 +2,18 @@
 // changes when umami's API does (novox/hq ADR 0039). Both this module's tools and its provisioner
 // import it; nothing outside umami does.
 
+import { readFileSync } from "node:fs";
+
+/** Read a secret from the file the mesh mounted it at, if the pointing env is set. */
+function readSecret(path: string | undefined): string | undefined {
+  if (!path) return undefined;
+  try {
+    return readFileSync(path, "utf8").trim() || undefined;
+  } catch {
+    return undefined;
+  }
+}
+
 export interface Website {
   id: string;
   name: string;
@@ -23,7 +35,7 @@ export class UmamiClient {
   static fromEnv(env: NodeJS.ProcessEnv = process.env): UmamiClient {
     const url = env.MESH_PROVISION_UMAMI_URL ?? env.UMAMI_URL;
     const username = env.UMAMI_USERNAME ?? "admin";
-    const password = env.UMAMI_ADMIN_PASSWORD;
+    const password = readSecret(env.MESH_UMAMI_ADMIN_PASSWORD_FILE) ?? env.UMAMI_ADMIN_PASSWORD;
     if (!url || !password) {
       throw new Error("UMAMI url or admin password is not set — umami's own code cannot reach it");
     }