fix: resolve hadolint lint issues (pin versions, remove redundant USER root)

Dockerfile

@@ -1,4 +1,4 @@
-FROM jcabillot/opencode:latest
+FROM jcabillot/opencode:1.16.2
 
 ARG OPENCHAMBER_WEB_VERSION=1.12.3
 
@@ -6,16 +6,15 @@ ENV NPM_CONFIG_UPDATE_NOTIFIER=false \
   NPM_CONFIG_LOGLEVEL=warn \
   NODE_ENV=production
 
-USER root
-
-RUN rm -rf /tmp/* \
-  && apt-get update \
-  && apt-get install -y --no-install-recommends python3 make g++ \
+RUN apt-get update \
+  && apt-get install -y --no-install-recommends \
+    python3=3.12* \
+    make=4.3* \
+    g++=14.2* \
   && rm -rf /var/lib/apt/lists/* \
   && npm install -g --no-fund --no-audit "@openchamber/web@${OPENCHAMBER_WEB_VERSION}" \
   && npm cache clean --force \
-  && openchamber --version \
-  && chown -R opencode:opencode /home/opencode
+  && openchamber --version
 
 WORKDIR /home/opencode/
 USER opencode