Add HTTP timeout to self-update downloads

[Copilot]

The self-update command uses http.Get() which has no timeout, allowing indefinite hangs on slow or unresponsive network connections.

Changes

• Created HTTP client with 30-second timeout for all update operations
• Applied to both GitHub API release check and binary download requests
• Added *.bak to .gitignore and removed tracked backup file

// Create HTTP client with timeout to prevent indefinite hangs
client := &http.Client{
    Timeout: 30 * time.Second,
}

// Use configured client instead of http.Get()
resp, err := client.Get("https://api.github.com/repos/" + repo + "/releases/latest")

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.