Re-add Slack MCP server when needed

## Overview
Re-add the Slack MCP server to our configuration when we need Slack integration in the future.

## Background
We've temporarily removed the Slack MCP server (see issue #277) to streamline our environment, but we anticipate needing Slack integration in the future. This issue serves as a placeholder for when we need to re-integrate Slack capabilities.

## Implementation Plan

1. **Update MCP Configuration**
- Add the Slack MCP server entry back to `mcp.json`:
```json
"slack": {
"command": "slack-mcp-wrapper.sh",
"args": [],
"env": {
"FASTMCP_LOG_LEVEL": "ERROR"
}
}
```
- Set up required environment variables in `.bash_secrets`

2. **Create/Restore Setup Scripts**
- Create or restore `setup-slack-mcp.sh` script
- Ensure it properly sets up the Docker container and dependencies

3. **Documentation Updates**
- Update README.md to add references to the Slack MCP server
- Add Slack back to the MCP Integrations table in documentation
- Add Slack-specific usage examples and instructions

4. **Testing**
- Verify Slack integration works with Amazon Q and other MCP clients
- Test basic Slack operations (message search, channel listing, etc.)

## Prerequisites
- Active Slack workspace with appropriate permissions
- Slack Bot token with necessary scopes
- Docker installed and running (for containerized deployment)

## Expected Benefits
- Enhanced communication capabilities through Slack integration
- Ability to search and retrieve Slack messages and content
- Improved workflow for teams that rely on Slack for communication

## Notes
This issue is linked to #277 (removal of Slack MCP server) and should be implemented when we have a specific need for Slack integration in our workflow.

When Slack integration is needed, first review issue #277 and the current mcp.json configuration. Restore the Slack entry, configure .bash_secrets, create or restore setup-slack-mcp.sh, update README.md and its MCP Integrations table, then verify the listed Slack operations with Amazon Q or another MCP client.

Written by the indexing model from the issue text.