clean: one RUN, no custom port

Dockerfile

@@ -7,11 +7,11 @@ WORKDIR /app
 COPY gleam.toml manifest.toml ./
 COPY src/ ./src/
 
-RUN gleam deps download && gleam build --target erlang
+RUN gleam deps download && \
+    gleam build --target erlang && \
+    adduser -D -H spasteg && \
+    chown -R spasteg:spasteg /app
 
-RUN adduser -D -H spasteg && chown -R spasteg:spasteg /app
-
-ENV PORT=3000
 EXPOSE 3000
 
 USER spasteg