fix: exclure backend/node_modules du .dockerignore et simplifier Dockerfile

.dockerignore

@@ -1,4 +1,6 @@
 node_modules
+backend/node_modules
+frontend/node_modules
 npm-debug.log
 .git
 .gitignore

Dockerfile

@@ -5,20 +5,13 @@ WORKDIR /app
 # Copy package files
 COPY backend/package*.json ./
 
-# Install dependencies with verbose output for debugging
-RUN echo "Installing dependencies..." && \
-    npm install --production && \
-    echo "Dependencies installed successfully" && \
-    npm list --production && \
-    npm cache clean --force
+# Install dependencies cleanly
+RUN npm install --production
 
 # Copy application code
 COPY backend/src ./src
 COPY frontend ./frontend
 
-# Verify express was installed
-RUN ls -la node_modules | grep express || echo "WARNING: express not found in node_modules"
-
 EXPOSE 4001
 
 CMD ["node", "src/server.js"]