refactor: split src into domain / application / infrastructure layers

Replace the history-driven lib/ + utils/ split with DDD layers:
- domain/: aggregate, repositories, value objects, pure parsers/format
- application/: feed-service, email-processor, feed-fetcher, stats
- infrastructure/: logging, auth, KV/R2 adapters, HTTP, framework glue

Pure file relocation; imports updated mechanically. Behaviour unchanged.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

src/application/feed-fetcher.ts

@@ -0,0 +1,36 @@
+import { Env, FeedConfig, EmailData } from "../types";
+import { MAX_FEED_ITEMS } from "../config/constants";
+import { FeedRepository } from "../domain/feed-repository";
+import { FeedId } from "../domain/value-objects/feed-id";
+
+export interface FeedData {
+  feedConfig: FeedConfig;
+  emails: EmailData[];
+}
+
+export async function fetchFeedData(
+  feedId: string,
+  env: Env,
+): Promise<FeedData | null> {
+  const repo = FeedRepository.from(env);
+  const id = FeedId.fromTrusted(feedId);
+
+  const feedMetadata = await repo.getMetadata(id);
+  if (!feedMetadata) return null;
+
+  const feedConfig = (await repo.getConfig(id)) ?? {
+    title: `Newsletter Feed ${feedId}`,
+    description: "Converted email newsletter",
+    language: "en",
+    created_at: Date.now(),
+  };
+
+  const emailRefs = feedMetadata.emails.slice(0, MAX_FEED_ITEMS);
+  const emails: EmailData[] = [];
+  for (const ref of emailRefs) {
+    const data = await repo.getEmail(ref.key);
+    if (data) emails.push(data);
+  }
+
+  return { feedConfig, emails };
+}