Final Dockerfile fix: Explicitly copy index.html path

Dockerfile

@@ -22,9 +22,18 @@ COPY requirements.txt .
 RUN pip install --no-cache-dir --upgrade pip && \
     pip install --no-cache-dir -r requirements.txt
 
+# --- Diagnostic step: List contents of /app before copying index.html ---
+# This command will output the contents of the /app directory in the build logs.
+# It can help diagnose if an unexpected 'file' is already present.
+RUN echo "Contents of /app before copying index.html:"
+RUN ls -la /app
+# --- End Diagnostic step ---
+
 # Copy the application files
 COPY app.py .
-COPY index.html .  # <--- ADDED THIS LINE to copy the HTML file
+# Explicitly copy index.html to /app/index.html to avoid any ambiguity with '.'
+# This is the primary change to address "cannot copy to non-directory: .../app/file"
+COPY index.html /app/index.html
 
 # Create a non-root user for security
 RUN useradd --create-home --shell /bin/bash app && \