chore: prepare package publishing metadata

- Add Gitea workflow for tagged package releases.
- Move package metadata into pyproject.toml.
- Bump the package version to 3.0.2.
- Define optional extras for dotenv, MongoDB, Redis, and Trio Redis.
- Keep setup.py as a minimal setuptools entry point.
- Disable universal wheel output for Python 3 only builds.

.gitea/workflows/publish.yml

@@ -0,0 +1,28 @@
+name: Build & Publish Package
+
+on:
+  push:
+    tags:
+      - "v*.*.*"
+  workflow_dispatch:
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v5
+
+      - name: Build package
+        run: uv build
+
+      - name: Publish to Gitea
+        run: |
+          uv publish \
+            --publish-url "${{ vars.REGISTRY_URL }}/api/packages/${{ github.repository_owner }}/pypi" \
+            --username "${{ github.repository_owner }}" \
+            --password "${{ secrets.ACTION_ACCESS_TOKEN }}"