REUSE-WP-0019-T03: add Forgejo Actions workflows (part 2 of prior commit)

The .forgejo/workflows/ files and doc updates described in 4862ed6 didn't
actually get staged there (git add silently skipped them after an earlier
pathspec miss on the already-deleted .gitea file) -- committing them now.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.forgejo/workflows/recompose-fallback.yaml

@@ -0,0 +1,29 @@
+# Scheduled fallback recompose trigger (REUSE-WP-0019-T03 design principle 3:
+# "degrade to schedule" if the org-level webhook is unavailable or misses an
+# event). The webhook (POST /v1/webhooks/forgejo) is the primary path; this
+# just guarantees the hub's composed index doesn't go stale indefinitely if a
+# webhook delivery is ever missed.
+name: Recompose Fallback
+
+on:
+  schedule:
+    - cron: "17 */6 * * *"
+  workflow_dispatch:
+
+jobs:
+  recompose:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Trigger hub recompose
+        env:
+          REUSE_SURFACE_TOKEN: ${{ secrets.REUSE_SURFACE_TOKEN }}
+        run: |
+          set -eu
+          apt-get update -qq
+          apt-get install -y -qq curl >/dev/null
+          status=$(curl -sS -o /tmp/compose.json -w '%{http_code}' \
+            -X POST "https://reuse.coulomb.social/v1/federated/compose" \
+            -H "Authorization: Bearer ${REUSE_SURFACE_TOKEN}")
+          echo "status=${status}"
+          cat /tmp/compose.json
+          [ "${status}" = "200" ]