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 <noreply@anthropic.com>

src/routes/admin.tsx

@@ -998,7 +998,7 @@ app.post(
       const { title, description } = c.req.valid("json");
 
       // Quick-edit: only title/description, expiry untouched.
-      const result = await editFeedDetails(env, FeedId.fromTrusted(feedId), {
+      const result = await editFeedDetails(env, FeedId.unchecked(feedId), {
         title,
         description,
       });