ci: migrate rpm changelog generation to reusable action

Replace the local .gitea/scripts/generate-rpm-changelog.sh with the
shared composite action at https://git.lair.cafe/actions/rpm-changelog@v1.
Behaviour is identical — collect commits since the previous v* tag,
filter bump-version and merge noise, prepend a dated entry to the
spec — but the logic now lives in one place that other projects can
consume.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -82,7 +82,10 @@ jobs:
           sed -i "s/^Version:.*/Version:        ${VERSION}/" cortex.spec
 
       - name: Generate changelog entry
-        run: bash .gitea/scripts/generate-rpm-changelog.sh cortex.spec "${{ steps.version.outputs.VERSION }}"
+        uses: https://git.lair.cafe/actions/rpm-changelog@v1
+        with:
+          spec: cortex.spec
+          version: ${{ steps.version.outputs.VERSION }}
 
       - name: Generate source tarball
         run: |
@@ -139,7 +142,10 @@ jobs:
           sed -i "s/^Version:.*/Version:        ${VERSION}/" neuron.spec
 
       - name: Generate changelog entry
-        run: bash .gitea/scripts/generate-rpm-changelog.sh neuron.spec "${{ steps.version.outputs.VERSION }}"
+        uses: https://git.lair.cafe/actions/rpm-changelog@v1
+        with:
+          spec: neuron.spec
+          version: ${{ steps.version.outputs.VERSION }}
 
       - name: Generate source tarball
         run: |