fix: Replace gh CLI with direct Gitea API calls (curl)

Root cause found via SSH log analysis (actions_log/.../2326.log):
  'gh release create' failed with exit code 127 (command not found).
  The act_runner Docker image used for jobs does not ship the
  GitHub CLI (gh), so any step relying on it fails immediately.

Fix: Replace gh CLI calls with direct Gitea REST API calls using
curl, which is available in the base image:
  1. POST /repos/{repo}/releases -- create release, parse id via python3
  2. POST /repos/{repo}/releases/{id}/assets -- upload artifact as multipart

This removes the gh CLI dependency entirely and matches how
deploy-prod.yml already talks to Gitea (curl + REST API).

.gitea/workflows/prepare-release.yml

@@ -125,26 +125,39 @@ jobs:
         env:
           VERSION: ${{ steps.metadata.outputs.version }}
           COMMIT: ${{ steps.metadata.outputs.commit }}
-          GITHUB_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
         run: |
           ARTIFACT="quantengine_${VERSION}.tar.gz"
+          API="https://gitea.taxbaik.com/api/v1"
+          REPO="kjh2064/QuantEngineByItz"
 
-          echo "Checking artifact..."
-          ls -lh "$ARTIFACT" || echo "⚠️ Artifact not found: $ARTIFACT"
+          test -s "$ARTIFACT" || { echo "ERROR: artifact missing: $ARTIFACT"; exit 1; }
 
-          echo ""
-          echo "Checking gh CLI..."
-          which gh || echo "⚠️ gh CLI not found"
-          gh version || echo "⚠️ gh version failed"
+          echo "Creating release $VERSION via Gitea API..."
+          RELEASE_JSON=$(curl -sf -X POST \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/json" \
+            -d "{\"tag_name\":\"${VERSION}\",\"name\":\"Release ${VERSION}\",\"body\":\"Release Version: ${VERSION} | Commit: ${COMMIT}\",\"target_commitish\":\"main\"}" \
+            "${API}/repos/${REPO}/releases")
 
-          echo ""
-          echo "Creating release..."
-          gh release create "$VERSION" "$ARTIFACT" \
-            --title "Release $VERSION" \
-            --notes "Release Version: $VERSION | Commit: ${COMMIT}" \
-            --repo kjh2064/QuantEngineByItz
+          RELEASE_ID=$(echo "$RELEASE_JSON" | python3 -c "import sys,json; print(json.load(sys.stdin)['id'])")
+
+          if [ -z "$RELEASE_ID" ] || [ "$RELEASE_ID" = "null" ]; then
+            echo "ERROR: Failed to create release"
+            echo "$RELEASE_JSON"
+            exit 1
+          fi
+
+          echo "✓ Release created: $VERSION (id: $RELEASE_ID)"
+
+          echo "Uploading artifact..."
+          curl -sf -X POST \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: multipart/form-data" \
+            -F "attachment=@${ARTIFACT}" \
+            "${API}/repos/${REPO}/releases/${RELEASE_ID}/assets?name=${ARTIFACT}" \
+            -o /dev/null
 
-          echo "✓ Release created: $VERSION"
           echo "✓ Artifact attached: $ARTIFACT"
 
   notification: