Complete DISCTL-WP-0002-T01: Forgejo off-Gitea mirror

Create private coulomb/disaster-control on forgejo.coulomb.social,
add mirror sync docs and tools/sync-mirror.sh, update registers and
README. Mark T01 done.

AssetRegister.yaml

@@ -372,8 +372,7 @@ assets:
     recovery_path:
       method: git clone from mirror or dump restore
     status: operational
-    gaps:
-      - "disaster-control not mirrored off primary Gitea (DISCTL-WP-0002-T01)"
+    gaps: []
 
   - id: asset-state-hub
     name: Custodian State Hub
@@ -390,12 +389,18 @@ assets:
     tier: T1
     owner: Bernd
     host: gitea.coulomb.social
-    backup: git push only
+    mirror:
+      url: https://forgejo.coulomb.social/coulomb/disaster-control
+      host: railiance01
+      remote: forgejo-remote:coulomb/disaster-control.git
+    backup: git push to origin + mirror sync
     recovery_path:
-      method: git clone from mirror (not yet configured)
-    status: at_risk
-    gaps:
-      - "No off-Gitea mirror (DISCTL-WP-0002-T01)"
+      method: git clone from Forgejo mirror; see docs/mirror-sync.md
+    backup_schedule: after each push to origin (./tools/sync-mirror.sh)
+    status: operational
+    references:
+      - docs/mirror-sync.md
+      - tools/sync-mirror.sh
 
   # ── T2 Runtime platforms ─────────────────────────────────────────────────────