add validation and unified schemas

Dockerfile

@@ -18,13 +18,10 @@ COPY ui/src ./src
 RUN npx shadow-cljs release app
 
 # Stage 2: the server.
-FROM clojure:openjdk-11-tools-deps
+# JDK 21+ is required by the MCP server (plumcp runs on virtual threads).
+FROM clojure:temurin-21-tools-deps
 
-RUN sed -i \
-    -e 's|deb.debian.org/debian|archive.debian.org/debian|g' \
-    -e '/security.debian.org/d' \
-    /etc/apt/sources.list \
-    && apt-get update && apt-get install -y --no-install-recommends curl \
+RUN apt-get update && apt-get install -y --no-install-recommends curl \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /app