win: add curl-style install script (#14178)

This adds a new powershell install script suitable for running via

  irm https://ollama.com/install.ps1 | iex

If you download the script and run '-?' it reports basic usage
information, as well as usage examples for common customization
options.  The script is signed as part of the release process
to ensure it can run on a typically configured Windows system.

This does not include doc updates - we can merge those after a release
ships to avoid user confusion.

scripts/install.sh

@@ -35,6 +35,8 @@ case "$ARCH" in
     *) error "Unsupported architecture: $ARCH" ;;
 esac
 
+VER_PARAM="${OLLAMA_VERSION:+?version=$OLLAMA_VERSION}"
+
 ###########################################
 # macOS
 ###########################################
@@ -49,11 +51,7 @@ if [ "$OS" = "Darwin" ]; then
         exit 1
     fi
 
-    if [ -n "${OLLAMA_VERSION:-}" ]; then
-        DOWNLOAD_URL="https://github.com/ollama/ollama/releases/download/${OLLAMA_VERSION}/Ollama-darwin.zip"
-    else
-        DOWNLOAD_URL="https://github.com/ollama/ollama/releases/latest/download/Ollama-darwin.zip"
-    fi
+    DOWNLOAD_URL="https://ollama.com/download/Ollama-darwin.zip${VER_PARAM}"
 
     if pgrep -x Ollama >/dev/null 2>&1; then
         status "Stopping running Ollama instance..."
@@ -103,8 +101,6 @@ case "$KERN" in
     *) ;;
 esac
 
-VER_PARAM="${OLLAMA_VERSION:+?version=$OLLAMA_VERSION}"
-
 SUDO=
 if [ "$(id -u)" -ne 0 ]; then
     # Running as root, no need for sudo