fix: support single group lookup and allow partial updates in group tools

[Tyagiquamar]

This PR improves group tool capabilities and input handling in the Requestly MCP server:

1. Single Group Lookup in get_groups: Added groupId parameter to get_groups schema and routed it through buildResourceUrl('groups', groupId) with URL-encoding and path-traversal protection.
2. Partial Updates in update_group: Made name optional and removed hardcoded default values (status: 'Active', isFavourite: false) from updateGroup schema so partial group updates don't overwrite existing status or favourite state.
3. Clean Payload Framing in create_group: Explicitly constructed the payload object to prevent extra or internal arguments from leaking into the upstream API body.
4. Schema Correction: Marked ruleId as required in updateRuleSchemas base fields.
5. Unit Tests: Added test coverage for group tools (create_group, get_groups for all & single group lookup, update_group partial updates, and delete_group).

[coderabbitai]

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[Tyagiquamar]

I have read the CLA Document and I hereby sign the CLA