feat(journal): outbound trails-to-trails follows (social-federation §6)

Tasks 6.1–6.6. A local user can follow a user on another trails
instance: WebFinger-resolve the handle, verify the target runs
trails.cool via NodeInfo — checked against the ACTOR IRI's host, never
the handle's domain (split-domain constraint) — record a Pending
follow row, deliver a signed Follow. The §4 inbox listeners already
settle (Accept) or drop (Reject) the row.

- federation-outbound.server.ts: followRemoteActor / cancelRemoteFollow
  (Undo delivery) / listOutgoingRemoteFollows. Network steps (lookup,
  NodeInfo, delivery) injectable for offline integration tests.
  Software allowlist: trails-cool.
- /follows/outgoing: follow-by-handle form + pending/accepted list +
  cancel; linked from the feed empty state; i18n en+de. Remote actors
  have no local profile page, so the remote Pending state lives here
  (the profile Pending button from locked accounts covers local).
- /.well-known/trails-cool now publishes software: trails-cool (6.2).
- Clear 4xx codes: invalid_handle, local_handle, remote_resolve_failed,
  not_trails (6.3).
- Tests: handle-parser + allowlist units; integration suite for the
  Pending lifecycle (create/idempotent/refuse-non-trails/refuse-
  unresolvable/own-host/cancel+Undo) with injected network deps; e2e
  anonymous-redirect guard for the new page.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

e2e/social.test.ts

@@ -47,6 +47,11 @@ test.describe("Social follows + /feed", () => {
     await expect(page).toHaveURL(/\/auth\/login/, { timeout: 10000 });
   });
 
+  test("/follows/outgoing redirects anonymous visitors to login", async ({ page }) => {
+    await page.goto("/follows/outgoing");
+    await expect(page).toHaveURL(/\/auth\/login/, { timeout: 10000 });
+  });
+
   test("/follows/requests redirects to /notifications?tab=requests", async ({ page, browser }) => {
     // The route was folded into the Notifications page as a tab. The
     // 301 still resolves; for anonymous visitors the notifications