Add Vulkan support for AMD GPUs alongside NVIDIA/CUDA

- Add build.sh script with nvidia/vulkan arguments (default: nvidia)
- Create backend abstraction: ModelBackend base class
- Implement NvidiaBackend using HuggingFace Transformers
- Implement VulkanBackend using llama-cpp-python with GGUF models
- Add separate requirements files for nvidia and vulkan backends
- Add --backend argument with auto/nvidia/vulkan options
- Add Vulkan-specific options: --n-gpu-layers, --n-ctx
- Make procname import optional
- Update README with comprehensive Vulkan usage instructions
- Add Vulkan troubleshooting section
- Add GGUF model recommendations

The application now supports:
- NVIDIA GPUs via PyTorch/Transformers (HuggingFace models)
- AMD GPUs via llama-cpp-python/Vulkan (GGUF models)

build.sh

+#!/bin/bash
+# Build script for CoderAI - Supports NVIDIA (CUDA) and Vulkan (AMD GPUs) backends
+# Usage: ./build.sh [nvidia|vulkan]
+# Default: nvidia
+
+set -e
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+BLUE='\033[0;34m'
+NC='\033[0m' # No Color
+
+# Determine backend
+BACKEND="${1:-nvidia}"
+BACKEND=$(echo "$BACKEND" | tr '[:upper:]' '[:lower:]')
+
+if [[ "$BACKEND" != "nvidia" && "$BACKEND" != "vulkan" ]]; then
+    echo -e "${RED}Error: Invalid backend '$BACKEND'${NC}"
+    echo "Usage: ./build.sh [nvidia|vulkan]"
+    echo "  nvidia  - Use PyTorch with CUDA for NVIDIA GPUs"
+    echo "  vulkan  - Use llama-cpp-python with Vulkan for AMD GPUs"
+    exit 1
+fi
+
+echo -e "${BLUE}========================================${NC}"
+echo -e "${BLUE}  CoderAI Build Script${NC}"
+echo -e "${BLUE}  Backend: ${GREEN}$BACKEND${NC}"
+echo -e "${BLUE}========================================${NC}"
+echo ""
+
+# Check Python version
+PYTHON_VERSION=$(python3 --version 2>&1 | grep -oP '\d+\.\d+' | head -1)
+REQUIRED_VERSION="3.8"
+
+if [ "$(printf '%s\n' "$REQUIRED_VERSION" "$PYTHON_VERSION" | sort -V | head -n1)" != "$REQUIRED_VERSION" ]; then
+    echo -e "${RED}Error: Python 3.8+ required, found $PYTHON_VERSION${NC}"
+    exit 1
+fi
+
+echo -e "${GREEN}✓ Python version: $PYTHON_VERSION${NC}"
+
+# Create virtual environment if it doesn't exist
+VENV_DIR="venv"
+if [ ! -d "$VENV_DIR" ]; then
+    echo -e "${YELLOW}Creating virtual environment...${NC}"
+    python3 -m venv "$VENV_DIR"
+fi
+
+# Activate virtual environment
+echo -e "${YELLOW}Activating virtual environment...${NC}"
+source "$VENV_DIR/bin/activate"
+
+# Upgrade pip
+echo -e "${YELLOW}Upgrading pip...${NC}"
+pip install --upgrade pip
+
+echo ""
+echo -e "${BLUE}Installing dependencies for $BACKEND backend...${NC}"
+echo ""
+
+if [ "$BACKEND" = "nvidia" ]; then
+    # NVIDIA/CUDA backend
+    echo -e "${YELLOW}Installing PyTorch with CUDA support...${NC}"
+    pip install "torch>=2.0.0" "torchvision>=0.15.0" "torchaudio>=2.0.0"
+    
+    echo -e "${YELLOW}Installing NVIDIA-specific requirements...${NC}"
+    pip install -r requirements-nvidia.txt
+    
+    echo ""
+    echo -e "${GREEN}========================================${NC}"
+    echo -e "${GREEN}  NVIDIA/CUDA build complete!${NC}"
+    echo -e "${GREEN}========================================${NC}"
+    echo ""
+    echo "Usage:"
+    echo "  source venv/bin/activate"
+    echo "  python coderai --model <huggingface-model-name>"
+    echo ""
+    echo "Example:"
+    echo "  python coderai --model microsoft/DialoGPT-medium"
+    echo ""
+    
+elif [ "$BACKEND" = "vulkan" ]; then
+    # Vulkan backend
+    echo -e "${YELLOW}Installing llama-cpp-python with Vulkan support...${NC}"
+    
+    # Check for required Vulkan development libraries
+    if ! pkg-config --exists vulkan 2>/dev/null; then
+        echo -e "${YELLOW}Warning: Vulkan development libraries not found via pkg-config${NC}"
+        echo -e "${YELLOW}You may need to install Vulkan drivers and SDK:${NC}"
+        echo "  Debian/Ubuntu: sudo apt install libvulkan-dev vulkan-tools"
+        echo "  Fedora: sudo dnf install vulkan-loader-devel vulkan-tools"
+        echo "  Arch: sudo pacman -S vulkan-headers vulkan-icd-loader"
+        echo ""
+        echo -e "${YELLOW}Attempting installation anyway...${NC}"
+    fi
+    
+    # Install llama-cpp-python with Vulkan support
+    # CMAKE_ARGS is used to enable Vulkan during compilation
+    CMAKE_ARGS="-DGGML_VULKAN=ON" pip install llama-cpp-python --no-cache-dir
+    
+    echo -e "${YELLOW}Installing Vulkan-specific requirements...${NC}"
+    pip install -r requirements-vulkan.txt
+    
+    echo ""
+    echo -e "${GREEN}========================================${NC}"
+    echo -e "${GREEN}  Vulkan build complete!${NC}"
+    echo -e "${GREEN}========================================${NC}"
+    echo ""
+    echo "Usage:"
+    echo "  source venv/bin/activate"
+    echo "  python coderai --model <path-to-gguf-model> --backend vulkan"
+    echo ""
+    echo "Example:"
+    echo "  python coderai --model ./phi-3-mini-4k-instruct-q4_k_m.gguf --backend vulkan"
+    echo ""
+    echo "Note: For Vulkan, you need to use GGUF format models."
+    echo "      Download from: https://huggingface.co/models?search=gguf"
+    echo ""
+fi
+
+# Create .backend file to track which backend was used
+echo "$BACKEND" > .backend
+
+echo -e "${GREEN}Build completed successfully!${NC}"
+echo ""
+echo "To activate the environment in the future, run:"
+echo "  source venv/bin/activate"

requirements-nvidia.txt

+# FastAPI and server dependencies
+fastapi>=0.104.0
+uvicorn[standard]>=0.24.0
+pydantic>=2.5.0
+
+# ML dependencies (transformers-based for NVIDIA/CUDA)
+transformers>=4.35.0
+accelerate>=0.24.0
+
+# System resource detection
+psutil>=5.9.0
+procname>=0.3.0  # optional - for setting process name
+
+# Optional: for better performance with NVIDIA GPUs
+bitsandbytes>=0.41.0
+sentencepiece>=0.1.99
+protobuf>=3.20.0
+
+# Optional: Flash Attention 2 for faster inference on supported NVIDIA GPUs
+# Requires specific CUDA versions and may need manual installation
+# Install with: pip install flash-attn --no-build-isolation
+# flash-attn>=2.5.0

requirements-vulkan.txt

+# FastAPI and server dependencies
+fastapi>=0.104.0
+uvicorn[standard]>=0.24.0
+pydantic>=2.5.0
+
+# llama-cpp-python is installed by build.sh with Vulkan support
+# CMAKE_ARGS="-DGGML_VULKAN=ON" pip install llama-cpp-python --no-cache-dir
+
+# System resource detection
+psutil>=5.9.0
+procname>=0.3.0  # optional - for setting process name
+
+# HuggingFace Hub for downloading GGUF models
+huggingface-hub>=0.19.0
+
+# No PyTorch needed for Vulkan backend - llama-cpp handles everything