feat: add devcontainer/nix support and refactor into modules

- Add .devcontainer/devcontainer.json for Podman development
- Add shell.nix for Nix users
- Refactor monolithic main.cpp into modular components:
  - parser: argument parsing
  - validator: configuration validation
  - converter: ffmpeg command building/execution
- Update Makefile with proper dependencies and test target
- Simplify build.sh to use make
- Update README with development environment docs

build.sh

@@ -1,96 +1,10 @@
 #!/bin/bash
 
-set -e  # Exit immediately if a command exits with a non-zero status
-set -u  # Treat unset variables as an error when substituting
-set -o pipefail  # Prevent errors in a pipeline from being masked
+set -e
 
-# Function to install dependencies for Debian-based systems
-install_debian_dependencies() {
-    echo "Installing dependencies for Debian-based systems..."
-    sudo apt-get update
-    sudo apt-get install -y build-essential ffmpeg || {
-        echo "Failed to install dependencies for Debian-based systems."
-        exit 1
-    }
-}
+echo "Building DaVinci Video Converter..."
 
-# Function to install dependencies for Red Hat-based systems
-install_redhat_dependencies() {
-    echo "Installing dependencies for Red Hat-based systems..."
-    sudo dnf install -y gcc-c++ ffmpeg make || {
-        echo "Failed to install dependencies for Red Hat-based systems."
-        exit 1
-    }
-}
-
-# Function to install dependencies for Arch Linux
-install_arch_dependencies() {
-    echo "Installing dependencies for Arch Linux..."
-    sudo pacman -S --noconfirm base-devel ffmpeg || {
-        echo "Failed to install dependencies for Arch Linux."
-        exit 1
-    }
-}
-
-# Function to install dependencies for openSUSE
-install_opensuse_dependencies() {
-    echo "Installing dependencies for openSUSE..."
-    sudo zypper install -y gcc-c++ ffmpeg make || {
-        echo "Failed to install dependencies for openSUSE."
-        exit 1
-    }
-}
-
-# Function to install dependencies for Alpine Linux
-install_alpine_dependencies() {
-    echo "Installing dependencies for Alpine Linux..."
-    sudo apk add --no-cache g++ ffmpeg make || {
-        echo "Failed to install dependencies for Alpine Linux."
-        exit 1
-    }
-}
-
-# Check the package manager and install dependencies accordingly
-if [ -f /etc/debian_version ]; then
-    install_debian_dependencies
-elif [ -f /etc/redhat-release ]; then
-    install_redhat_dependencies
-elif [ -f /etc/arch-release ]; then
-    install_arch_dependencies
-elif [ -f /etc/os-release ]; then
-    . /etc/os-release
-    case "$ID" in
-        opensuse*)
-            install_opensuse_dependencies
-            ;;
-        alpine)
-            install_alpine_dependencies
-            ;;
-        *)
-            echo "Unsupported distribution: $ID. Please install the required packages manually."
-            exit 1
-            ;;
-    esac
-else
-    echo "Unsupported distribution. Please install the required packages manually."
-    exit 1
-fi
-
-# Build the project
-echo "Building the project..."
+make clean
 make
 
-# Check if the build was successful
-if [ $? -eq 0 ]; then
-    echo "Build completed successfully."
-else
-    echo "Build failed. Please check the output for errors."
-    exit 1
-fi
-
-# Install the application
-echo "Installing the application..."
-make install
-
-# Inform the user about the executable
-echo "You can run the application using 'davinci-convert'"
+echo "Build complete! Binary: ./davinci-video-converter"