Add tomli backport (#475)

### What kind of change does this PR introduce?

* Adds a missing backport dependency for Python3.10
* Do not allow-unsafe CI pins

### Does this PR introduce a breaking change?

No.

Author: Zeitsperre

CI/requirements_ci.in

@@ -4,5 +4,6 @@ exceptiongroup==1.2.2
 flit==3.10.1
 pip==25.0
 pylint==3.3.4
+tomli==2.2.1
 tox-gh==1.5.0
 tox==4.24.1

CI/requirements_ci.txt

@@ -2,7 +2,7 @@
 # This file is autogenerated by pip-compile with Python 3.10
 # by the following command:
 #
-#    pip-compile --allow-unsafe --generate-hashes --output-file=CI/requirements_ci.txt CI/requirements_ci.in
+#    pip-compile --generate-hashes --output-file=CI/requirements_ci.txt CI/requirements_ci.in
 #
 annotated-types==0.7.0 \
     --hash=sha256:1f02e8b43a8fbbc3f3e0d4f0f4bfc8131bcb4eebe8849b8e5c773f3a1c582a53 \
@@ -438,6 +438,7 @@ tomli==2.2.1 \
     --hash=sha256:ece47d672db52ac607a3d9599a9d48dcb2f2f735c6c2d1f34130085bb12b112a \
     --hash=sha256:f4039b9cbc3048b2416cc57ab3bda989a6fcf9b36cf8937f01a6e731b64f80d7
     # via
+    #   -r CI/requirements_ci.in
     #   deptry
     #   pylint
     #   pyproject-api
@@ -493,10 +494,7 @@ wcwidth==0.2.13 \
     --hash=sha256:72ea0c06399eb286d978fdedb6923a9eb47e1c486ce63e9b4e64fc18303972b5
     # via prompt-toolkit
 
-# The following packages are considered to be unsafe in a requirements file:
-pip==25.0 \
-    --hash=sha256:8e0a97f7b4c47ae4a494560da84775e9e2f671d415d8d828e052efefb206b30b \
-    --hash=sha256:b6eb97a803356a52b2dd4bb73ba9e65b2ba16caa6bcb25a7497350a4e5859b65
-    # via
-    #   -r CI/requirements_ci.in
-    #   flit
+# WARNING: The following packages were not pinned, but pip requires them to be
+# pinned when the requirements file includes hashes and the requirement is not
+# satisfied by a package already installed. Consider using the --allow-unsafe flag.
+# pip