refactor: move release changelog workflow to releases repo

The workflow triggers on `release: published` which only fires from the
default branch. Since the releases repo default branch is `main` (not
`master` synced from server), the workflow never triggered from here.

Move it to nextcloud-releases/server where it belongs alongside other
release infrastructure. Also adds HTML changelog generation and attaches
it as a release asset for the marketing team.

Signed-off-by: John Molakvoæ (skjnldsv) <skjnldsv@protonmail.com>

.github/workflows/generate-release-changelog.yml

@@ -1,104 +0,0 @@
-# SPDX-FileCopyrightText: 2025 Nextcloud GmbH and Nextcloud contributors
-# SPDX-License-Identifier: MIT
-
-name: Generate changelog on release
-
-on:
-  release:
-    types: [published]
-
-permissions:
-  contents: write
-
-jobs:
-  changelog_generate:
-    runs-on: ubuntu-latest
-
-    # Only allowed to be run on nextcloud-releases repositories
-    if: ${{ github.repository_owner == 'nextcloud-releases' }}
-
-    steps:
-      - name: Check actor permission
-        uses: skjnldsv/check-actor-permission@69e92a3c4711150929bca9fcf34448c5bf5526e7 # v3.0
-        with:
-          require: write
-
-      - name: Checkout github_helper
-        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
-        with:
-          persist-credentials: false
-          repository: nextcloud/github_helper
-          path: github_helper
-
-      - name: Checkout server
-        uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
-        with:
-          persist-credentials: false
-          path: server
-          fetch-depth: 0
-
-      - name: Get previous tag
-        shell: bash
-        run: |
-          cd server
-          # Print all tags
-          git log --decorate --oneline | egrep 'tag: ' | sed -r 's/^.+tag: ([^,\)]+)[,\)].+$/\1/g'
-          # Get the current tag
-          TAGS=$(git log --decorate --oneline | egrep 'tag: ' | sed -r 's/^.+tag: ([^,\)]+)[,\)].+$/\1/g')
-          CURRENT_TAG=$(echo "$TAGS" | head -n 1)
-
-          # If current tag is the first beta, we use the previous major RC1
-          if echo "$CURRENT_TAG" | grep -q 'beta1'; then
-            MAJOR=$(echo "$CURRENT_TAG" | sed -E 's/^v([0-9]+).*/\1/')
-            PREV=$((MAJOR - 1))
-            PREVIOUS_TAG="v${PREV}.0.0rc1"
-          # Get the previous tag - filter pre-releases only if current tag is stable
-          elif echo "$CURRENT_TAG" | grep -q 'rc\|beta\|alpha'; then
-            # Current tag is pre-release, don't filter
-            PREVIOUS_TAG=$(echo "$TAGS" | sed -n '2p')
-          else
-            # Current tag is stable, filter out pre-releases
-            PREVIOUS_TAG=$(echo "$TAGS" | grep -v 'rc\|beta\|alpha' | sed -n '2p')
-          fi
-
-          echo "CURRENT_TAG=$CURRENT_TAG" >> $GITHUB_ENV
-          echo "PREVIOUS_TAG=$PREVIOUS_TAG" >> $GITHUB_ENV
-
-      # Since this action only runs on nextcloud-releases, ignoring is okay
-      - name: Verify current tag # zizmor: ignore[template-injection]
-        run: |
-         if [ "${{ github.ref_name }}" != "${{ env.CURRENT_TAG }}" ]; then
-           echo "Current tag does not match the release tag. Exiting."
-           exit 1
-         fi
-
-      - name: Set up php 8.2
-        uses: shivammathur/setup-php@bf6b4fbd49ca58e4608c9c89fba0b8d90bd2a39f # v2.35.5
-        timeout-minutes: 5
-        with:
-          php-version: 8.2
-          coverage: none
-          ini-file: development
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-      - name: Set credentials
-        run: |
-          echo '{"username": "github-actions"}' > github_helper/credentials.json
-
-      # Since this action only runs on nextcloud-releases, ignoring is okay
-      - name: Generate changelog between ${{ env.PREVIOUS_TAG }} and ${{ github.ref_name }} # zizmor: ignore[template-injection]
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: |
-          cd github_helper/changelog
-          composer install
-          php index.php generate:changelog --no-bots --format=forum server ${{ env.PREVIOUS_TAG }} ${{ github.ref_name }} > changelog.md
-
-      # Since this action only runs on nextcloud-releases, ignoring is okay
-      - name: Set changelog to release # zizmor: ignore[template-injection]
-        env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-        run: |
-         cd server
-         gh release edit ${{ github.ref_name }} --notes-file "../github_helper/changelog/changelog.md" --title "${{ github.ref_name }}"