docs: warn about archived reference servers (#4785)

[FOWEPJF255]

Description

Docs update for #4785:

• Add a warning under Archived that archived packages are unmaintained and provide no security guarantees.
• Document archived-server reporting / support status in SECURITY.md.
• Replace Claude Desktop config examples that still used archived @modelcontextprotocol/server-github and server-postgres with an active mcp-server-time example, and note not to configure archived packages in new setups.

npm deprecate message rewrites still need package-publisher rights (maintainer-owned), as noted in the issue.

Publishing Your Server

N/A 鈥?documentation only; not adding a server to the README listing.

Server Details

• Server: N/A (repo README / SECURITY)
• Changes to: documentation

Motivation and Context

Archived reference servers still see large weekly npm installs while the default npm deprecation text points at npm support. This PR makes the main README and SECURITY.md carry the archive/security message for users who land here, and stops recommending archived packages in client config examples. Fixes #4785 (docs portion).

How Has This Been Tested?

Docs-only; reviewed rendered Markdown locally. No server runtime changes.

Breaking Changes

None. Example configs no longer show archived github/postgres packages; that matches their archived status.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Protocol Documentation
• My changes follows MCP security best practices
• I have updated the server's README accordingly
• I have tested this with an LLM client
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have documented all environment variables and configuration options

Additional context

Local branch: docs/archived-servers-4785 on fork FOWEPJF255/servers.