refactor: rename email-server-worker to email-worker

Rename directory from email-server-worker to email-worker for clarity and brevity. Update all references in CLAUDE.md documentation.

email-worker/tests/__mocks__/prom-client.ts

@@ -0,0 +1,29 @@
+import { LabelValues } from "prom-client";
+
+export class Counter {
+    public inc() {
+
+    }
+}
+
+export class Histogram<T extends string> {
+    startTimer(labels?: LabelValues<T>): (labels?: LabelValues<T>) => void {
+        return((labels?: LabelValues<T>) => { });
+    }
+}
+
+class Register {
+    public setDefaultLabels(labels: Object) {
+
+    }
+
+    public metrics(): Promise<string> {
+        return(Promise.resolve(""));
+    }
+
+    public get contentType() {
+        return("");
+    }
+}
+
+export const register = new Register();