build(elixir): add dev container

.devcontainer/Dockerfile

@@ -0,0 +1,47 @@
+# Use the official Elixir image with OTP 26 and Elixir 1.15
+FROM elixir:1.15-otp-26-slim
+
+# Install system dependencies
+RUN apt-get update && apt-get install -y \
+    git \
+    curl \
+    build-essential \
+    inotify-tools \
+    postgresql-client \
+    sudo \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Node.js 20 (needed for assets compilation)
+RUN curl -fsSL https://deb.nodesource.com/setup_20.x | bash - \
+    && apt-get install -y nodejs
+
+# Create a non-root user
+RUN groupadd --gid 1000 vscode \
+    && useradd --uid 1000 --gid vscode --shell /bin/bash --create-home vscode \
+    && echo 'vscode ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
+
+# Set the working directory
+WORKDIR /workspace
+
+# Copy the project files
+COPY --chown=vscode:vscode . /workspace
+
+# Install Hex and Rebar
+RUN mix local.hex --force && \
+    mix local.rebar --force
+
+# Switch to vscode user
+USER vscode
+
+# Install Phoenix
+RUN mix archive.install hex phx_new --force
+
+# Set environment variables
+ENV MIX_ENV=dev
+ENV PHX_SERVER=true
+
+# Expose port 4000 for Phoenix
+EXPOSE 4000
+
+# Default command
+CMD ["tail", "-f", "/dev/null"]