feat(install): Add arch-specific install scripts and docs for systemd setup

[PDJ107]

Summary

Add minimal installation scripts for amd64 and arm64 that download a GitHub
release tarball, install the binary, create a systemd unit, and start the service.
Include README docs for install environment variable.

Changes

• scripts/install_amd64.sh, scripts/install_arm64.sh
• README: quick start, env vars, service management guide

How to Test

1. On amd64 (or arm64) host:

   chmod +x scripts/install_amd64.sh
   sudo MORPHER_CONTROLLER_IP=<controller-ip> ./scripts/install_amd64.sh

2. Verify:

   systemctl status morpher-agent --no-pager
   journalctl -u morpher-agent -e --no-pager

[Copilot]

Pull Request Overview

This PR adds arch-specific installation scripts for amd64 and arm64 architectures that automate the download, installation, and systemd service setup for the morpher-agent. The changes include comprehensive README documentation with installation instructions, environment variable configuration, and service management guidance.

• Added automated installation scripts for both amd64 and arm64 architectures
• Enhanced README with quick start guide, environment variables documentation, and service management instructions
• Integrated systemd service creation and automatic startup functionality

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

File	Description
scripts/install_amd64.sh	Installation script for x86_64 architecture with GitHub release download and systemd setup
scripts/install_arm64.sh	Installation script for ARM64 architecture with GitHub release download and systemd setup
README.md	Added comprehensive installation documentation, quick start guide, and service management instructions

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