[connectors] Generic HTTP/REST connector — call any API as configuration

[serge-ivo]

Child of #94, child of #84.

The connector children today are GitHub / Google Sheets / Gmail — specific systems. The lead-finder needs Google Places, and the broader goal (#94) needs any REST API to be usable without code.

Do

A configurable generic connector: a connector instance = { baseUrl, auth (none | apiKey-from-vault | bearer | oauth-grant), defaultHeaders }, exposing a parameterized http_request tool:

• method, path/template, query, headers, JSON body — all with {{param}} interpolation from pipeline/settings inputs.
• auth from the key vault (envelope crypto / user_api_keys), never inline.
• response mapping: JSONPath-ish extraction → typed fields (e.g. places[].{id,displayName.text,websiteUri,addressComponents}).
• pagination descriptor (nextPageToken / offset / cursor) so a source step can fan out pages.

Acceptance

• Google Places searchText + searchNearby callable purely by configuring a generic-HTTP connector (key from vault) — no bespoke code.
• Callable via runtime, MCP, and POST …/tools/http_request (per [connectors] Generic tool-call API + MCP auto-generation #87).
• Auth never exposed to creator code/logs; audited.