updated docker error

Dockerfile

@@ -1,11 +1,35 @@
 # Flutter web build, served as static files by nginx.
 #
 # Dokploy builds this repo with its Dockerfile provider, so the image does the
-# whole job: pull the Flutter SDK, compile the web bundle, hand the output to a
-# web server. Nothing from the build stage survives into the final image but
+# whole job: install the Flutter SDK, compile the web bundle, hand the output to
+# a web server. Nothing from the build stage survives into the final image but
 # build/web.
+#
+# The SDK comes from the official archive at a pinned version rather than from a
+# `flutter:stable` image: those images trail the real stable channel, and the
+# one tagged stable ships a Dart older than the SDK floor in pubspec.yaml, so
+# `pub get` refuses to resolve. Keep FLUTTER_VERSION in step with the toolchain
+# the app is developed against.
 
-FROM ghcr.io/cirruslabs/flutter:stable AS build
+FROM debian:bookworm-slim AS build
+
+ARG FLUTTER_VERSION=3.44.9
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+        ca-certificates curl git unzip xz-utils \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN curl -fsSL "https://storage.googleapis.com/flutter_infra_release/releases/stable/linux/flutter_linux_${FLUTTER_VERSION}-stable.tar.xz" \
+    | tar -xJ -C /opt
+
+ENV PATH="/opt/flutter/bin:${PATH}"
+
+# The SDK is a git checkout owned by a different user than the one building, so
+# without this every flutter command dies on git's dubious-ownership check.
+RUN git config --global --add safe.directory /opt/flutter \
+    && flutter config --disable-analytics \
+    && flutter precache --web
 
 WORKDIR /app