🔖 Prepare release of v3.1.0 (#648)

## Description

This PR prepares the release of v3.1.0.

## Checklist:

- [x] The pull request only contains commits that are focused and
relevant to this change.
- [x] ~~I have added appropriate tests that cover the new/changed
functionality.~~
- [x] ~~I have updated the documentation to reflect these changes.~~
- [x] I have added entries to the changelog for any noteworthy
additions, changes, fixes, or removals.
- [x] I have added migration instructions to the upgrade guide (if
needed).
- [x] The changes follow the project's style guidelines and introduce no
new warnings.
- [x] The changes are fully tested and pass the CI checks.
- [x] I have reviewed my own code changes.

Author: denialhaag

CHANGELOG.md

@@ -9,21 +9,25 @@ This project adheres to [Semantic Versioning], with the exception that minor rel
 
 ## [Unreleased]
 
+## [3.1.0] - 2025-07-11
+
+_If you are upgrading: please see [`UPGRADING.md`](UPGRADING.md#310)._
+
 ### Changed
 
 - **Breaking**: ⬆️ Bump minimum required MQT Core version to `3.1.0` ([#646]) ([**@denialhaag**])
 - **Breaking**: ⬆️ Bump minimum required `pybind11` version to `3.0.0` ([#646]) ([**@denialhaag**])
 - ♻️ Move the C++ code for the Python bindings to the top-level `bindings` directory ([#618]) ([**@denialhaag**])
 - ♻️ Move all Python code (no tests) to the top-level `python` directory ([#618]) ([**@denialhaag**])
-- **Breaking**: ZX-calculus checker now reports that it can't handle circuits with non-garbage ancilla qubits ([#512]) ([**@pehamTom**])
+- **Breaking**: 💥 ZX-calculus checker now reports that it can't handle circuits with non-garbage ancilla qubits ([#512]) ([**@pehamTom**])
 
 ### Deprecated
 
 - 🗑️ Deprecate the `mode` argument of `generate_profile()` and the `ancilla_mode` argument of `verify_compilation()` ([#626]) ([**@denialhaag**])
 
 ### Fixed
 
-- Fixed bug in ZX-calculus checker for circuits without data qubits ([#512]) ([**@pehamTom**])
+- 🐛 Fix bug in ZX-calculus checker for circuits without data qubits ([#512]) ([**@pehamTom**])
 
 ## [3.0.0] - 2025-05-05
 
@@ -53,7 +57,8 @@ _📚 Refer to the [GitHub Release Notes] for previous changelogs._
 
 <!-- Version links -->
 
-[unreleased]: https://github.com/munich-quantum-toolkit/qcec/compare/v3.0.0...HEAD
+[unreleased]: https://github.com/munich-quantum-toolkit/qcec/compare/v3.1.0...HEAD
+[3.1.0]: https://github.com/munich-quantum-toolkit/qcec/compare/v3.0.0...v3.1.0
 [3.0.0]: https://github.com/munich-quantum-toolkit/qcec/compare/v2.8.2...v3.0.0
 [2.8.2]: https://github.com/munich-quantum-toolkit/qcec/releases/tag/v2.8.2
 

UPGRADING.md

@@ -4,6 +4,8 @@ This document describes breaking changes and how to upgrade. For a complete list
 
 ## [Unreleased]
 
+## [3.1.0]
+
 Even tough this is not a breaking change, it is worth mentioning to developers of MQT QCEC that all Python code (except tests) has been moved to the top-level `python` directory.
 Furthermore, the C++ code for the Python bindings has been moved to the top-level `bindings` directory.
 
@@ -37,6 +39,12 @@ MQT QCEC now requires CMake 3.24 or higher.
 Most modern operating systems should have this version available in their package manager.
 Alternatively, CMake can be conveniently installed from PyPI using the [`cmake`](https://pypi.org/project/cmake/) package.
 
-[MQT SyReC]: https://github.com/cda-tum/mqt-syrec
-[unreleased]: https://github.com/munich-quantum-toolkit/core/compare/v3.0.0...HEAD
+<!-- Version links -->
+
+[unreleased]: https://github.com/munich-quantum-toolkit/qcec/compare/v3.1.0...HEAD
+[3.1.0]: https://github.com/munich-quantum-toolkit/qcec/compare/v3.0.0...v3.1.0
 [3.0.0]: https://github.com/munich-quantum-toolkit/qcec/compare/v2.8.2...v3.0.0
+
+<!-- Other links -->
+
+[MQT SyReC]: https://github.com/cda-tum/mqt-syrec