docs: Gitea PyPI install paths and publish automation

Add make package-check/publish-gitea, tag-triggered Gitea Actions workflow,
PACKAGE_RELEASE.md, and update README/GETTING_STARTED install instructions
for the Coulomb registry (v1.1.0+).

.gitea/workflows/publish-python-package.yml

@@ -0,0 +1,37 @@
+name: Publish Python package
+
+on:
+  push:
+    tags:
+      - "v*"
+  workflow_dispatch:
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out source
+        uses: actions/checkout@v4
+
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+
+      - name: Install packaging tools
+        run: python -m pip install --upgrade build twine
+
+      - name: Build distributions
+        run: python -m build
+
+      - name: Validate distributions
+        run: python -m twine check dist/*
+
+      - name: Upload to Gitea PyPI
+        env:
+          TWINE_USERNAME: ${{ secrets.GITEA_PACKAGE_USER }}
+          TWINE_PASSWORD: ${{ secrets.GITEA_PACKAGE_TOKEN }}
+        run: >-
+          python -m twine upload
+          --repository-url https://gitea.coulomb.social/api/packages/coulomb/pypi
+          dist/*