fix: make SAM3 Docker dependencies opt-in

Author: Somnusochi

backend/.dockerignore

@@ -1,5 +1,6 @@
 # Python
 .venv/
+.venv-sam3/
 sam3-venv/
 __pycache__/
 *.pyc
@@ -32,4 +33,13 @@ Thumbs.db
 # Data
 uploads/
 training_runs/
+trained_models/
 model/
+pretrained/
+external_models/
+import_chunks/
+import_progress/
+*.db
+*.sqlite
+*.sqlite3
+*.log

backend/Dockerfile

@@ -1,57 +1,54 @@
-# Build stage
+# Build stage — SAM3 support is opt-in to keep default image size small
 FROM python:3.12-slim as builder
 
 WORKDIR /app
 
-# Install build dependencies
+ARG INSTALL_SAM3=false
+
 RUN apt-get update && apt-get install -y --no-install-recommends \
     libpq-dev gcc \
     && rm -rf /var/lib/apt/lists/*
 
-# Install Python dependencies
 COPY requirements.txt requirements-sam3.txt ./
 RUN pip install --no-cache-dir --prefix=/install -r requirements.txt \
-    && python -m venv /sam3-venv \
-    && /sam3-venv/bin/pip install --no-cache-dir -r requirements-sam3.txt
+    && mkdir -p /sam3-venv \
+    && if [ "$INSTALL_SAM3" = "true" ]; then \
+         python -m venv /sam3-venv \
+         && /sam3-venv/bin/pip install --no-cache-dir -r requirements-sam3.txt; \
+       fi
 
 # Production stage
 FROM python:3.12-slim
 
 WORKDIR /app
 
-# Install runtime dependencies only
+ARG INSTALL_SAM3=false
+
 RUN apt-get update && apt-get install -y --no-install-recommends \
     libpq5 ffmpeg \
     && rm -rf /var/lib/apt/lists/*
 
-# Copy decord stub (decord is Linux-only, not needed by LocateAnything-3B)
 COPY decord_stub.py /usr/local/lib/python3.12/site-packages/decord.py
 
-# Copy Python packages from builder
 COPY --from=builder /install /usr/local
-# Copy SAM3 venv
 COPY --from=builder /sam3-venv /app/sam3-venv
 
-# Create non-root user and data directories
 RUN useradd -m -u 1000 appuser \
     && mkdir -p /app/uploads /app/model /app/training_runs \
     && chown -R appuser:appuser /app
 USER appuser
 
-# Copy application code
 COPY --chown=appuser:appuser app ./app
 COPY --chown=appuser:appuser sam3_server.py .
 COPY --chown=appuser:appuser alembic.ini .
 COPY --chown=appuser:appuser alembic ./alembic
 
-# Set environment variables
 ENV PYTHONPATH=/app \
     PYTHONUNBUFFERED=1 \
     PYTHONDONTWRITEBYTECODE=1
 
 EXPOSE 8000 8002
 
-# Health check
 HEALTHCHECK --interval=30s --timeout=10s --start-period=40s --retries=3 \
     CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/api/health')"