Six modules take their secrets from files; the rest say precisely why not

From the survey of every env-file secret (ADR 0086, issue 041): amqp-ping,
minio, mongodb and grafana use the _FILE twin their software honours;
mesh-catalog and model-usage read DATABASE_URL_FILE (a file the mesh
templates, mounted where only the runtime reads it); grafana's secret files
belong to its own account. Two dead deliveries removed: a line nothing read
in amqp-email-forwarder, and mailu's secret.env on four containers that
never read it. The 25 exceptions that remain carry the surveyed reason —
convertible and awaiting a bed, convertible through a generated config file,
the application's own code, or not convertible.

modules/mesh-catalog/store.ts

@@ -1,3 +1,4 @@
+import { readFileSync } from "node:fs";
 // The module graph (novox/hq ADR 0070, ADR 0072).
 //
 // **This graph links module-versions to each other and knows nothing about nodes.** Which machine
@@ -138,7 +139,9 @@ export class Graph {
   private constructor(private readonly pool: PgPool) {}
 
   static fromEnv(env: NodeJS.ProcessEnv = process.env): Graph {
-    const url = env["DATABASE_URL"];
+    // As a file first (novox/hq ADR 0086): the connection string carries the password, and the
+    // mesh writes it where only this process reads it; the plain variable remains for a hand-run.
+    const url = env["DATABASE_URL"] ?? readMaybe(env["DATABASE_URL_FILE"]);
     if (!url) {
       throw new Error(
         "no DATABASE_URL: the catalogue holds the module graph and cannot hold it in memory, " +
@@ -390,3 +393,13 @@ export class Graph {
     await this.pool.end();
   }
 }
+
+/** The content of a file the environment names, its line ending gone — or undefined when it names none. */
+function readMaybe(path: string | undefined): string | undefined {
+  if (!path) return undefined;
+  try {
+    return readFileSync(path, "utf8").replace(/\r?\n$/, "");
+  } catch {
+    return undefined;
+  }
+}