Replace softprops release action with native Gitea API release

softprops/action-gh-release@v1 is not mirrored on the Forgejo action
mirror, which fatally aborted the job at action-download. Create the
release via the Gitea REST API using the built-in GITHUB_TOKEN and
upload both pack artifacts directly.

.gitea/workflows/build-pack.yaml

@@ -137,10 +137,19 @@ jobs:
 
       - name: Release
         if: startsWith(github.ref, 'refs/tags/v')
-        uses: softprops/action-gh-release@v1
-        with:
-          files: |
-            SciCraft-Modrinth.mrpack
-            SciCraft-CurseForge.zip
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          set -e
+          TAG="${GITHUB_REF_NAME}"
+          API="https://git.mithraic.cloud/api/v1/repos/ad3laid3/SciCraft/releases"
+          AUTH="Authorization: token ${{ secrets.GITHUB_TOKEN }}"
+          RELEASE_JSON=$(curl -sS -X POST "$API" \
+            -H "$AUTH" \
+            -H "Content-Type: application/json" \
+            -d "{\"tag_name\":\"$TAG\",\"name\":\"SCICRAFT $TAG\",\"body\":\"Automated release built from Gitea Actions.\"}")
+          RELEASE_ID=$(printf '%s' "$RELEASE_JSON" | python3 -c "import sys,json; print(json.load(sys.stdin)['id'])")
+          for f in SciCraft-Modrinth.mrpack SciCraft-CurseForge.zip; do
+            curl -sS -X POST "$API/$RELEASE_ID/assets?name=$(basename "$f")" \
+              -H "$AUTH" \
+              -F "attachment=@$f"
+            echo "Uploaded $f"
+          done