fix: Split pip install into smaller layers for Docker Hub

Author: ambsd

Dockerfile

@@ -54,11 +54,21 @@ RUN useradd -m -u 1000 heartmula && \
 # Copy backend requirements first for better caching
 COPY --chown=heartmula:heartmula backend/requirements.txt /app/backend/
 
-# Install Python dependencies
-RUN pip3 install --no-cache-dir --upgrade pip && \
-    pip3 install --no-cache-dir torch torchvision torchaudio --index-url https://download.pytorch.org/whl/cu121 && \
-    pip3 install --no-cache-dir -r /app/backend/requirements.txt && \
-    pip3 install --no-cache-dir bitsandbytes accelerate
+# Install Python dependencies in separate layers for smaller Docker Hub uploads
+# Layer 1: pip upgrade
+RUN pip3 install --no-cache-dir --upgrade pip
+
+# Layer 2: PyTorch (largest dependency ~800MB)
+RUN pip3 install --no-cache-dir torch --index-url https://download.pytorch.org/whl/cu121
+
+# Layer 3: torchvision and torchaudio
+RUN pip3 install --no-cache-dir torchvision torchaudio --index-url https://download.pytorch.org/whl/cu121
+
+# Layer 4: Other requirements
+RUN pip3 install --no-cache-dir -r /app/backend/requirements.txt
+
+# Layer 5: bitsandbytes and accelerate
+RUN pip3 install --no-cache-dir bitsandbytes accelerate
 
 # Copy backend code
 COPY --chown=heartmula:heartmula backend/ /app/backend/