Update API docs (developers.chameleon.io) with company search & filter options

[anton-ko]

• Document filters, filters_op, sort_by, sort_dir, and offset params on GET|POST /companies to expose full search and filter capabilities to API consumers
• Add two new request body examples (multi-property filter with filters_op: or, and sort by profile_count) to illustrate the new params in context
• Add a "Counting Companies" subsection documenting GET|POST /companies/count with its request params and response shape
• Note that only property and group filter kinds are supported for companies (unlike profile search which also supports event, tour, and survey)
• Note offset-based cursor pagination behavior when filters or sort_by is provided, contrasting with the standard before/after cursor used by the list endpoint

🤖 Chameleon dev for INFRA-414