Auth tokens: --token flag for serve-http

[omoshola-o]

Add --token <SECRET> flag to serve-http command.

Behavior

• Required header: Authorization: Bearer <token>
• Reject requests without valid token (MCP error -32803)
• Token source priority: CLI arg > AGENTIC_TOKEN env var > config file

Implementation

fn check_auth(req: &Request, expected: &str) -> Result<(), McpError> {
    let header = req.headers().get("Authorization")
        .ok_or(McpError::Unauthorized)?;
    let token = header.to_str()?.strip_prefix("Bearer ")
        .ok_or(McpError::Unauthorized)?;
    if token != expected {
        return Err(McpError::Unauthorized);
    }
    Ok(())
}

Usage

agentic-memory-mcp serve-http --port 8080 --token "secret123"

Part of #1