refactor: move KV repositories to infrastructure (Track P — points 2, 6c)

Make the domain stop depending on infrastructure ("imports point inward").

- Point 2: relocate the four KV adapters (FeedRepository, IconRepository,
  WebSubSubscriptionRepository, CountersRepository) from domain/ to
  infrastructure/, where the logger import is legitimate. The domain now keeps
  only the pure key schema (feed-keys.ts), the Feed aggregate and value objects;
  it imports nothing outward. Deliberately no hand-rolled 24-method port
  interface (YAGNI without DI) — relocation alone fixes the direction.
- Point 6c: EmailParser.extractFeedId now returns a validated FeedId value
  object instead of a raw string, so the most untrusted input (an inbound
  recipient address) is guarded at the parse boundary and no longer round-trips
  through FeedId.fromTrusted in the ingest path.

All import paths updated; CLAUDE.md source layout/KV-schema notes updated.
351 tests pass; tsc --noEmit clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/infrastructure/icon-repository.ts

@@ -0,0 +1,31 @@
+import { Env } from "../types";
+import { feedKeys } from "../domain/feed-keys";
+
+/**
+ * KV access for cached per-domain favicons (`icon:<domain>`). Entries may be
+ * positive (base64 bytes) or negative (a sentinel marking a failed fetch), and
+ * always carry a TTL — the cache's sole expiry mechanism.
+ */
+export class IconRepository {
+  constructor(private readonly kv: KVNamespace) {}
+
+  static from(env: Env): IconRepository {
+    return new IconRepository(env.EMAIL_STORAGE);
+  }
+
+  getText(domain: string): Promise<string | null> {
+    return this.kv.get(feedKeys.icon(domain), "text");
+  }
+
+  async getJson<T>(domain: string): Promise<T | null> {
+    return (await this.kv.get(feedKeys.icon(domain), {
+      type: "json",
+    })) as T | null;
+  }
+
+  async put(domain: string, value: string, ttlSeconds: number): Promise<void> {
+    await this.kv.put(feedKeys.icon(domain), value, {
+      expirationTtl: ttlSeconds,
+    });
+  }
+}