* feat: migrate extension framework to wxt
- Replace Plasmo entrypoints, messaging, and storage usage with WXT-compatible implementations
- Update workflows, build scripts, and locale paths for WXT outputs
- Switch store submission to wxt submit with optional dry-run input
* fix(ci): fallback to vars for submit credentials
- Resolve missing required config in submit workflow when values are stored in GitHub Variables instead of Secrets
- Keep existing secrets first and add vars fallback for Chrome, Firefox, and Edge credentials