Fix SAM2 installation for Docker build

Dockerfile

@@ -25,7 +25,16 @@ RUN pip install --no-cache-dir \
 
 # install all other dependencies
 COPY requirements.txt .
-RUN pip install --no-cache-dir -r requirements.txt
+
+# Install everything except SAM2
+RUN grep -v "facebookresearch/sam2" requirements.txt > requirements_no_sam.txt && \
+    pip install --no-cache-dir -r requirements_no_sam.txt
+
+# SAM2 officially requires torch>=2.5.1, but this project was
+# developed and validated with torch==2.4.1. Install SAM2 without dependency resolution to preserve the tested environment
+
+RUN pip install --no-cache-dir --no-deps \
+    git+https://github.com/facebookresearch/sam2.git@2b90b9f5ceec907a1c18123530e92e794ad901a4
 
 # copy backend code
 COPY . .