fix(ci): add fallback for GitHub API failures in release workflow (#388)

## Description

CI was failing on new module releases because there was no fallback to
gh api failures when there was no previous tag for the module was found.


https://github.com/coder/registry/actions/runs/17225186737/job/48868318539

<!-- Briefly describe what this PR does and why -->

## Type of Change

- [ ] New module
- [ ] Bug fix
- [ ] Feature/enhancement
- [ ] Documentation
- [X] Other

.github/workflows/release.yml

@@ -73,10 +73,15 @@ jobs:
             exit 0
           fi
           
-          FULL_CHANGELOG=$(gh api repos/:owner/:repo/releases/generate-notes \
-            --field tag_name="$CURRENT_TAG" \
-            --field previous_tag_name="$PREV_TAG" \
-            --jq '.body')
+          if [[ "$PREV_TAG" == release/* ]]; then
+            FULL_CHANGELOG=$(gh api repos/:owner/:repo/releases/generate-notes \
+              --field tag_name="$CURRENT_TAG" \
+              --field previous_tag_name="$PREV_TAG" \
+              --jq '.body')
+          else
+            echo "New module detected, skipping GitHub API"
+            FULL_CHANGELOG=""
+          fi
           
           MODULE_COMMIT_SHAS=$(git log --format="%H" --no-merges "$PREV_TAG..$CURRENT_TAG" -- "$MODULE_PATH")