Add install script, CI workflows, and release pipeline

- Install script: curl-pipe-sh installer that downloads the right
  binary for the user's OS/arch from GitHub Releases
- CI workflow: runs go vet + go test for both Go modules and builds
  the web app on push/PR
- Release workflow: goreleaser builds cross-platform binaries
  (linux/darwin, amd64/arm64) on version tags
- Node-agent defaults BETTERNAS_CONTROL_PLANE_URL to
  https://api.betternas.com so users only need username/password

scripts/install-betternas-node.sh

@@ -0,0 +1,70 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+repo="${BETTERNAS_NODE_REPO:-harivansh-afk/betterNAS}"
+binary_name="betternas-node"
+install_dir="${BETTERNAS_INSTALL_DIR:-$HOME/.local/bin}"
+version="${BETTERNAS_NODE_VERSION:-}"
+release_api_url="${BETTERNAS_NODE_RELEASE_API_URL:-https://api.github.com/repos/${repo}/releases/latest}"
+download_base_url="${BETTERNAS_NODE_DOWNLOAD_BASE_URL:-https://github.com/${repo}/releases/download}"
+
+if [[ -z "$version" ]]; then
+  version="$(
+    curl -fsSL "${release_api_url}" | \
+      python3 -c 'import json,sys; print(json.load(sys.stdin)["tag_name"])'
+  )"
+fi
+
+os_name="$(uname -s)"
+arch_name="$(uname -m)"
+
+case "$os_name" in
+  Darwin) os="darwin" ;;
+  Linux) os="linux" ;;
+  *)
+    echo "Unsupported OS: $os_name" >&2
+    exit 1
+    ;;
+esac
+
+case "$arch_name" in
+  x86_64|amd64) arch="amd64" ;;
+  arm64|aarch64) arch="arm64" ;;
+  *)
+    echo "Unsupported architecture: $arch_name" >&2
+    exit 1
+    ;;
+esac
+
+archive_name="${binary_name}_${version}_${os}_${arch}.tar.gz"
+download_url="${download_base_url}/${version}/${archive_name}"
+
+tmp_dir="$(mktemp -d)"
+cleanup() {
+  rm -rf "$tmp_dir"
+}
+trap cleanup EXIT
+
+echo "Downloading ${download_url}"
+curl -fsSL "$download_url" -o "${tmp_dir}/${archive_name}"
+
+mkdir -p "$install_dir"
+tar -xzf "${tmp_dir}/${archive_name}" -C "$tmp_dir"
+install -m 0755 "${tmp_dir}/${binary_name}" "${install_dir}/${binary_name}"
+
+cat <<EOF
+Installed ${binary_name} to ${install_dir}/${binary_name}
+
+If ${install_dir} is not in your PATH, add this to your shell profile:
+  export PATH="${install_dir}:\$PATH"
+
+Then run the node with:
+  BETTERNAS_USERNAME=your-username \\
+  BETTERNAS_PASSWORD=your-password \\
+  BETTERNAS_EXPORT_PATH=/path/to/export \\
+  BETTERNAS_NODE_DIRECT_ADDRESS=https://your-public-node-url \\
+  ${binary_name}
+
+The control plane defaults to https://api.betternas.com.
+EOF