feat: modernize Docker build and stabilize test suite

Dockerfile

@@ -1,7 +1,43 @@
-# https://docs.docker.com/engine/reference/builder/
+# BUILDER STAGE
+FROM python:3.12-slim AS builder
 
-FROM python:3.12
-COPY dist/*.whl .
+WORKDIR /build
+
+# Install Poetry and export plugin
+RUN pip install poetry==1.8.3
+
+# Copy dependency files
+COPY pyproject.toml poetry.lock README.md ./
+
+# Export requirements.txt from poetry.lock for robust pip installation
+# We use --without-hashes to avoid issues with some platforms/versions
+RUN poetry export -f requirements.txt --output requirements.txt --without-hashes
+
+# Copy source code
+COPY src/ ./src/
+
+# Build the wheel
+RUN poetry build --format=wheel
+
+# RUNNER STAGE
+FROM python:3.12-slim
+
+WORKDIR /app
+
+# Copy requirements and wheel from builder
+COPY --from=builder /build/requirements.txt .
+COPY --from=builder /build/dist/*.whl .
+
+# Install dependencies from the EXACT versions solved by Poetry
+RUN pip install -r requirements.txt
+# Install the application wheel
 RUN pip install *.whl
-# Ejecuta la función main() del módulo controller.kafka_app
+
+# Copy configurations
+COPY confs/ ./confs/
+
+# Set environment variables
+ENV PYTHONUNBUFFERED=1
+
+# Entrypoint for the Kafka application
 CMD ["python", "-m", "regression_model_template.controller.kafka_app"]