refactor(domain): make FeedId circulate through the domain and repository

FeedId is now the type of Feed.id and of every single-feed method on
FeedRepository; callers wrap raw strings via FeedId.fromTrusted at the
repository boundary. String-medium operations (URLs, logs, JSON,
list registry, email keys) stay string. Drop the redundant
generateFeedId wrapper in favour of FeedId.generate.

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

src/routes/hub.ts

@@ -8,6 +8,7 @@ import { waitUntilSafe } from "../utils/worker";
 import { DEFAULT_LEASE_SECONDS, MAX_LEASE_SECONDS } from "../config/constants";
 import { feedTopicPattern } from "../utils/urls";
 import { FeedRepository } from "../domain/feed-repository";
+import { FeedId } from "../domain/value-objects/feed-id";
 
 type AppEnv = { Bindings: Env };
 
@@ -74,7 +75,9 @@ hubRouter.post("/", async (c) => {
   const feedId = match[2];
 
   // Verify the feed exists before accepting any subscription
-  const feedConfig = await FeedRepository.from(env).getConfig(feedId);
+  const feedConfig = await FeedRepository.from(env).getConfig(
+    FeedId.fromTrusted(feedId),
+  );
   if (!feedConfig) {
     return c.text("Not Found: feed does not exist", 404);
   }