feat(journal): surface Fedify logs via LogTape console sink

Inbound Mastodon Follows are being rejected 401 (signature
verification) on staging and Fedify's diagnostics were invisible:
it logs through LogTape, which is silent until configured.

- Configure LogTape with a console sink for the 'fedify' category when
  the federation instance is built; level via FEDERATION_LOG_LEVEL
  (default info).
- Staging deploy sets FEDERATION_LOG_LEVEL=debug for the soak —
  signature-verification detail per request; dial down once proven.

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

.github/workflows/cd-staging.yml

@@ -131,6 +131,9 @@ jobs:
             # rollout 12.2). FEDERATION_KEY_ENCRYPTION_KEY comes from the
             # SOPS env decrypted above; previews never set this flag.
             echo "FEDERATION_ENABLED=true"
+            # Verbose Fedify logs during the soak (signature verification
+            # detail). Dial down to info once federation is proven out.
+            echo "FEDERATION_LOG_LEVEL=debug"
           } >> infrastructure/staging.env
 
       - name: Copy compose file + env to server