fix(feed): advertise WebSub hub in RSS/Atom body

Readers like FreshRSS discover the hub from <atom:link rel="hub"> in the
feed XML, not the HTTP Link header. Without it they never subscribe and
only refresh on cache expiry (~30 min) instead of receiving an instant
push when a new email arrives.

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

CHANGELOG.md

@@ -14,6 +14,11 @@ verbatim as the GitHub Release notes — so what you write here is what ships.
 
 ### Fixed
 
+- RSS and Atom feeds now advertise the WebSub hub inside the feed body
+  (`<atom:link rel="hub">`), not just in the HTTP `Link` header. Readers like
+  FreshRSS discover the hub from the XML, so they can now subscribe and receive
+  an instant push when a new email arrives instead of waiting up to the cache
+  `max-age` (30 min) to refresh.
 - Subscription-confirmation detection now recognises a confirm email whose CTA
   button carries the subscribe/subscription hint only in its visible text (e.g.
   "Yes, subscribe me to this mailing list.") over an opaque tracking-redirect

src/infrastructure/feed-generator.test.ts

@@ -130,6 +130,17 @@ describe("generateRssFeed", () => {
     expect(result).toContain(`${BASE_URL}/rss/${FEED_ID}`);
   });
 
+  it("advertises the WebSub hub in the RSS body", () => {
+    const result = generateRssFeed(
+      mockFeedConfig,
+      mockEmails,
+      BASE_URL,
+      FEED_ID,
+    );
+    expect(result).toContain('rel="hub"');
+    expect(result).toContain(`${BASE_URL}/hub`);
+  });
+
   it("includes email entries as <item> elements", () => {
     const result = generateRssFeed(
       mockFeedConfig,
@@ -280,6 +291,17 @@ describe("generateAtomFeed", () => {
     expect(result).toContain(`${BASE_URL}/atom/${FEED_ID}`);
   });
 
+  it("advertises the WebSub hub in the Atom body", () => {
+    const result = generateAtomFeed(
+      mockFeedConfig,
+      mockEmails,
+      BASE_URL,
+      FEED_ID,
+    );
+    expect(result).toContain('rel="hub"');
+    expect(result).toContain(`${BASE_URL}/hub`);
+  });
+
   it("includes rss alternate link", () => {
     const result = generateAtomFeed(
       mockFeedConfig,

src/infrastructure/feed-generator.ts

@@ -35,6 +35,10 @@ function buildFeed(
     // Public "website" for this feed: its own read URL (never the inbound address
     // or an auth-gated admin path, so the feed output leaks neither).
     link: `${baseUrl}/rss/${feedId}`,
+    // WebSub hub advertised in the feed body (<atom:link rel="hub">). Readers like
+    // FreshRSS discover the hub here, not from the HTTP Link header, so without it
+    // they never subscribe and only refresh on cache expiry.
+    hub: `${baseUrl}/hub`,
     language: feedConfig.language,
     updated: new Date(),
     generator: "kill-the-news",