Chore: Modernize project tooling

- Migrates packaging configuration from `setup.py` and `setup.cfg` to `pyproject.toml`.
- Drops support for Python 3.9 and updates the type hint syntax to use the `|` operator for `Union` and `Optional`, in line with Python 3.10+ features.
- Adds Python 3.14 to the CI test matrix.
- Switches the CI/CD workflows to use `uv` for dependency management instead of `pip`.

Author: google-labs-jules[bot]

.github/workflows/publish.yaml

@@ -11,7 +11,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@v4
-    - uses: astral-sh/setup-uv@v1
+    - uses: astral-sh/setup-uv@v7
     - name: Install dependencies
       run: uv pip install -e '.[release]'
     - name: Install Build Tool

.github/workflows/test.yaml

@@ -18,7 +18,7 @@ jobs:
 
         steps:
         - uses: actions/checkout@v4
-        - uses: astral-sh/setup-uv@v1
+        - uses: astral-sh/setup-uv@v7
         - name: Install Dependencies
           run: uv pip install -e '.[lint]'
         - name: Run Ruff Format
@@ -32,7 +32,7 @@ jobs:
 
         steps:
         - uses: actions/checkout@v4
-        - uses: astral-sh/setup-uv@v1
+        - uses: astral-sh/setup-uv@v7
         - name: Install Dependencies
           run: uv pip install -e '.[lint,test]'
         - name: Run MyPy
@@ -48,7 +48,7 @@ jobs:
 
         steps:
         - uses: actions/checkout@v4
-        - uses: astral-sh/setup-uv@v1
+        - uses: astral-sh/setup-uv@v7
           with:
               python-version: ${{ matrix.python-version }}
         - name: Install Dependencies
@@ -66,7 +66,7 @@ jobs:
 #
 #        steps:
 #        - uses: actions/checkout@v4
-#        - uses: astral-sh/setup-uv@v1
+#        - uses: astral-sh/setup-uv@v7
 #        - name: Install Dependencies
 #          run: uv pip install -e '.[test]'
 #        - name: Run Tests