refactor: separate Feed domain state from persistence DTO

Move four DDD tensions on the Feed aggregate to ground:

- #1 The aggregate now holds a domain FeedState (camelCase) instead of the
  snake_case FeedConfig DTO; infrastructure/feed-mapper.ts owns the
  FeedState<->FeedConfig/FeedListItem translation as the sole snake_case site
  outside the HTTP edge.
- #3 Replace the edit() recomputeExpiry control flag with a Lifetime VO:
  passing a lifetime recomputes expiry, omitting it preserves the current one
  (the dashboard quick-edit path).
- #4 Domain events carry their own feedId; dispatchFeedEvents centralizes the
  drain+dispatch in the application layer (no more manual pullEvents at call
  sites), keeping infra->application dependency direction intact.
- #6 Rename FeedId.fromTrusted to FeedId.unchecked to make the absence of
  revalidation explicit.

Adds Lifetime + feed-mapper round-trip tests. 353 tests green, tsc clean,
wrangler dry-run OK. Docs (CLAUDE.md) synced.

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

src/infrastructure/websub-subscription-repository.test.ts

@@ -5,7 +5,7 @@ import { FeedId } from "../domain/value-objects/feed-id";
 import type { Env, WebSubSubscription } from "../types";
 
 const mockEnv = () => createMockEnv() as unknown as Env;
-const fid = FeedId.fromTrusted("a.b.42");
+const fid = FeedId.unchecked("a.b.42");
 
 describe("WebSubSubscriptionRepository", () => {
   it("round-trips subscriptions and counts feeds with subscribers", async () => {