add release.sh: build + tag both version and latest, then push

Takes a version (e.g. 2.1), validates its format, runs docker build
once with both tags to skip a second build pass, then pushes both.
Warns on uncommitted changes but doesn't block.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

release.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -euo pipefail
+docker login docker-repo.hacker-net.de
+IMAGE="docker-repo.hacker-net.de/imap-mailfilter"
+
+if [[ $# -ne 1 ]]; then
+    echo "Usage: $0 <version>" >&2
+    echo "Beispiel: $0 2.1" >&2
+    exit 1
+fi
+
+VERSION="$1"
+
+if [[ ! "$VERSION" =~ ^[0-9]+(\.[0-9]+)*$ ]]; then
+    echo "Fehler: Version '$VERSION' hat kein gültiges Format (z.B. 2.1 oder 2.1.0)" >&2
+    exit 1
+fi
+
+# Warnung bei uncommitteten Änderungen (kein Abbruch)
+if [[ -d .git ]] && ! git diff-index --quiet HEAD -- 2>/dev/null; then
+    echo "Warnung: uncommittete Änderungen im Repo. Baue trotzdem." >&2
+    git status --short >&2
+    echo >&2
+fi
+
+echo "==> Baue $IMAGE:$VERSION und :latest"
+docker build \
+    -t "$IMAGE:$VERSION" \
+    -t "$IMAGE:latest" \
+    .
+
+echo "==> Pushe $IMAGE:$VERSION"
+docker push "$IMAGE:$VERSION"
+
+echo "==> Pushe $IMAGE:latest"
+docker push "$IMAGE:latest"
+
+echo
+echo "Release fertig: $IMAGE:$VERSION (und :latest)"