feat(contract): support campaign co-creation

[Fayedamz]

Summary
Implements campaign co-creation for issue #717 by allowing campaigns to have multiple creators who share ownership, decision-making, and revenue.
Changes
Adds ordered campaign creator lists and revenue shares in basis points.
Preserves backward compatibility with the existing single-creator create_campaign API.
Adds create_campaign_with_creators for multi-creator campaigns.
Requires every creator to authorize campaign creation.
Validates non-empty, unique creator lists with positive shares totaling 10,000 basis points.
Distributes successful campaign proceeds proportionally among creators after protocol fees.
Adds support for adding authorized co-creators before campaign success.
Adds creator and revenue-share query methods.
Preserves insurance-fee handling, campaign ID exhaustion protection, and milestone tracking.
Validation
cargo test --manifest-path contracts/Cargo.toml -p campaign-funding
Result: 51 tests passed, 0 failed
cargo fmt --manifest-path contracts/Cargo.toml --all
git diff --check

closes #717

[coderabbitai]

Important

• 🔍 Trigger review

This repository does not receive automatic reviews because it has fewer than 10 stars.

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f57c5aae-de98-4dc0-a9dc-209535edb0bf

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[Utilitycoder]

Please fix up the merge conflict and update your PR. Kindly ensure you offramp with Fundable at https://stellar.fundable.finance/offramp

[Utilitycoder]

Thanks for the work. Kindly ensure you offramp with Fundable at https://stellar.fundable.finance/offramp