feat(crowdfunding): implement token config and campaign creation fees

[petersdt]

Crowdfunding Configuration & Fee Collection

This PR implements the configuration logic for the crowdfunding contract, enabling dynamic control over the supported token and campaign creation fees.

Changes

• Configuration: Added admin functions to set the global crowdfunding token and creation fee.
• Fee Collection: Updated create_campaign to deduct the configured fee from the creator's balance before creating a campaign.
• Storage: Added persistent storage for crowdfunding_token, creation_fee, and admin.
• Events: Added new events CrowdfundingTokenSet, CreationFeeSet, and CreationFeePaid.
• Tests: Added comprehensive tests covering configuration updates, fee payments, insufficient balance checks, and non-admin access restrictions.

Verification

• Run cargo test crowdfunding_test to verify all 37 tests pass.
• Run cargo build --target wasm32-unknown-unknown --release to verify successful compilation.

closes #14

[Akshola00]

gm @petersdt pls include your test snapshots
great modularizing of test setup, makes it a lot easier to create a large change

[Akshola00]

ci is failing, please format your code

[martinvibes]

@petersdt pls there's no need to add back the test snap shots since it's an unnecessary file that amounts to making the codebase larger than expected

[martinvibes]

so fix conflict and don't push back the snapshots it's unncessary

[martinvibes]

LGTM!