Add simple poll contract example

[alexgduarte]

Summary

Adds a new simple-poll CosmWasm contract example.

The example lets any account create a poll, stores generated poll IDs, validates question and option limits, allows one vote per address, supports optional block-height closing, lets the poll creator or owner close a poll manually, and exposes config, poll, vote, and paginated poll-list queries.

This is intended as an original simple-tier contract example for bounty issue #11.

Validation

• cargo fmt --manifest-path simple-poll/Cargo.toml -- --check
• cargo test --manifest-path simple-poll/Cargo.toml --target-dir /private/tmp/codex-simple-poll-target (9 passed)
• git diff --cached --check

Bounty Contact

GitHub: @alexgduarte

Stablecoin payout details can be provided privately if accepted.