Fix Gleam module compilation - copy src directory and gleam.toml

- Add src directory to Dockerfile (contains Gleam source files)
- Add gleam.toml to Dockerfile (Gleam configuration)
- The mix compile alias already handles gleam_compile

This minimal change ensures Gleam files are available during the build
without modifying the compilation process.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile

@@ -32,6 +32,8 @@ RUN mix deps.get --only $MIX_ENV && \
 # Copy and compile application
 COPY config config
 COPY lib lib
+COPY src src
+COPY gleam.toml ./
 COPY assets assets
 COPY priv priv
 COPY rel rel