feat: add CHANGELOG.md and auto-create Gitea release on tag push

Release body now includes conventional-commit bullet points, a compare
link (prev_tag...current_tag) and a link to CHANGELOG.md for both the
GitHub release and a new Gitea release created via API.
GITEA_TOKEN secret must be added to GitHub repo secrets to enable
the Gitea release step.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/build-android.yml

@@ -103,6 +103,7 @@ jobs:
         run: |
           PREV_TAG=$(git tag --sort=-version:refname | grep -v "^${{ github.ref_name }}$" | head -1)
           echo "Previous tag: $PREV_TAG"
+          echo "prev_tag=$PREV_TAG" >> "$GITHUB_OUTPUT"
 
           FEATS=$(git log "${PREV_TAG}..HEAD" --pretty=format:"%s" --no-merges \
             | grep -E "^feat(\([^)]+\))?: " \
@@ -129,9 +130,45 @@ jobs:
             ## SheetHappens ${{ github.ref_name }}
 
             ${{ steps.changelog.outputs.changelog }}
+            [Full changelog](https://github.com/${{ github.repository }}/compare/${{ steps.changelog.outputs.prev_tag }}...${{ github.ref_name }}) · [CHANGELOG.md](https://github.com/${{ github.repository }}/blob/main/CHANGELOG.md)
+
             ### Installation
             1. Enable "Unknown sources" on the device
             2. Transfer the APK to the device and open it to install
           files: ${{ steps.apk.outputs.path }}
           draft: false
           prerelease: ${{ contains(github.ref_name, '-') }}
+
+      - name: Create Gitea Release
+        env:
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          TAG: ${{ github.ref_name }}
+          PREV_TAG: ${{ steps.changelog.outputs.prev_tag }}
+          CHANGELOG: ${{ steps.changelog.outputs.changelog }}
+          GH_REPO: ${{ github.repository }}
+        run: |
+          if [ -z "$GITEA_TOKEN" ]; then
+            echo "GITEA_TOKEN not set — skipping Gitea release"
+            exit 0
+          fi
+
+          BODY="## SheetHappens ${TAG}
+
+          ${CHANGELOG}
+
+          [Full changelog](https://homegit.gyozamancave.fr/billisdead/SheetHappens/compare/${PREV_TAG}...${TAG}) · [CHANGELOG.md](https://homegit.gyozamancave.fr/billisdead/SheetHappens/raw/branch/main/CHANGELOG.md)
+
+          ### Installation
+          Download the APK from the [GitHub release](https://github.com/${GH_REPO}/releases/tag/${TAG}), enable \"Unknown sources\" on the device and install."
+
+          curl -sf -X POST \
+            -H "Authorization: token ${GITEA_TOKEN}" \
+            -H "Content-Type: application/json" \
+            "https://homegit.gyozamancave.fr/api/v1/repos/billisdead/SheetHappens/releases" \
+            -d "{
+              \"tag_name\": \"${TAG}\",
+              \"name\": \"SheetHappens ${TAG}\",
+              \"body\": $(printf '%s' "$BODY" | jq -Rs .),
+              \"draft\": false,
+              \"prerelease\": $([ "${TAG#*-}" != "${TAG}" ] && echo true || echo false)
+            }"