release: 1.0.0 changelog and a job that creates the Gitea release

CHANGELOG.md in Portuguese, from the project history. The release job builds its
notes from the matching section. The new files are excluded from the image hash,
so the published image is reused. README points at the Gitea repository.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

scripts/release-notes.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+# Imprime as notas de uma release: a imagem publicada e a seção do CHANGELOG.md
+# daquela versão (ou o log de commits desde a tag anterior, se não houver seção).
+#
+#   scripts/release-notes.sh v1.2.3 git.exemplo.com/dono/projeto
+set -euo pipefail
+
+tag=${1:?uso: release-notes.sh <tag> <imagem>}
+image=${2:?uso: release-notes.sh <tag> <imagem>}
+version=${tag#v}
+
+echo "## Imagem"
+echo
+echo '```'
+echo "$image:$version"
+echo '```'
+echo
+
+section=""
+if [ -f CHANGELOG.md ]; then
+  section=$(awk -v head="## [$version]" '
+    index($0, head) == 1 { found = 1; next }
+    found && /^## \[/ { exit }
+    found && /^\[[^]]+\]: / { next }
+    found { print }
+  ' CHANGELOG.md)
+fi
+
+if [ -n "$(printf '%s' "$section" | tr -d '[:space:]')" ]; then
+  printf '%s\n' "$section"
+else
+  previous=$(git describe --tags --abbrev=0 "$tag^" 2>/dev/null || true)
+  echo "## Mudanças${previous:+ desde $previous}"
+  echo
+  git log --no-merges --format='- %s (%h)' "${previous:+$previous..}$tag"
+fi