feat: Upgrade devcontainer setup (#14419)

* Feat: Upgrade devcontainer

* Style: Format devcontainer.json

* Chore: Remove settings from devcontainer

* chore: add shebang

* chore: fix shellcheck

---------

Co-authored-by: Bünyamin Olgun <buenyamin.olgun@cancom.de>
Co-authored-by: Jason Rasmussen <jason@rasm.me>

.devcontainer/Dockerfile

@@ -1,2 +1,16 @@
 ARG BASEIMAGE=mcr.microsoft.com/devcontainers/typescript-node:22@sha256:9791f4aa527774bc370c6bd2f6705ce5a686f1e6f204badd8dfaacce28c631ae
 FROM ${BASEIMAGE}
+
+# Flutter SDK
+# https://flutter.dev/docs/development/tools/sdk/releases?tab=linux
+ENV FLUTTER_CHANNEL="stable"
+ENV FLUTTER_VERSION="3.24.5"
+ENV FLUTTER_HOME=/flutter
+ENV PATH=${PATH}:${FLUTTER_HOME}/bin
+
+# Flutter SDK
+RUN mkdir -p ${FLUTTER_HOME} \
+  && curl -C - --output flutter.tar.xz https://storage.googleapis.com/flutter_infra_release/releases/${FLUTTER_CHANNEL}/linux/flutter_linux_${FLUTTER_VERSION}-${FLUTTER_CHANNEL}.tar.xz \
+  && tar -xf flutter.tar.xz --strip-components=1 -C ${FLUTTER_HOME} \
+  && rm flutter.tar.xz \
+  && chown -R 1000:1000 ${FLUTTER_HOME}