Postman / Bruno Collection for Contract RPC Endpoints

[Luluameh]

Background
QA engineers and integrators need a ready-made API collection to manually test all contract entry points against Testnet without writing code.
Goal
Create a fully-configured Bruno (or Postman) collection that covers every public contract function, with example payloads and environment variables for Testnet and Mainnet.
Acceptance Criteria

• Collection file at docs/api/skillsphere.bru (or .postman_collection.json).
• Environment files for testnet and mainnet with contract IDs and RPC URLs.
• Each request includes a description, example payload, and expected response.
• At least one automated test script per request (status 200, valid response shape).
  Key Files
  docs/api/skillsphere.bru, docs/api/testnet.env, docs/api/mainnet.env