Add project status registry contract example

[ryanll]

Summary

• Add an original simple-tier project-status-registry CosmWasm example contract
• Include owner-managed project creation, status updates, ownership transfer, single-record query, and paginated list query
• Add a README walkthrough and link the new example from the root README

Bounty

This is submitted for the simple contract bounty in #11.

Contact for payout coordination: GitHub @ryanll. Stablecoin payout details can be provided when the maintainers review/accept the bounty submission.

Validation

• git diff --check passed locally
• cargo test could not be run in this environment because cargo/rustc are not installed
• Docker-based test attempt could not run because the local Docker daemon is not running