CI/CD: Duplicate issue detector and auto labelling as "Duplicate"

**Problem**: Contributors must manually search through many existing issues before creating a new one, which is time-consuming and often leads to duplicate reports.

**How**: Add automated duplicate detection using a GitHub bot (semantic matching) and a lightweight GitHub Action to flag similar existing issues on creation.

****Impact**: it will mark that issue duplicate so that maintainer don't have to waste too much time**

Notes: Automation will only suggest possible duplicates (no auto-closing, or auto-closing depends on choice) .

@Zahnentferner what's your view on this? Please assign

No files, tests, or entry points are named in the issue. Start by reviewing the repository's GitHub automation configuration and determine how duplicate suggestions, Duplicate labeling, and the optional auto-close behavior should be scoped. Done means similar issues are flagged and labeled without unintended auto-closing.

Written by the indexing model from the issue text.