Add security contact verification

[mayasimi]

Resolves #255 Summary

• add on-chain security contact fields, proof CID storage, and exposed verification status
• add project metadata schema support for security_contact
• add tests for contact update, proof submission, proof reset on contact change, invalid proof, and auth failures
• fix existing CI blockers found on the clean branch: fee event signature calls, maintainer hydration on get_project, and a rating property-test precondition
• run cargo fmt so the full crate passes CI formatting

Tests

• cargo fmt --check
• cargo test -p dongle-contract security_contact
• cargo test -p dongle-contract
• cargo clippy -p dongle-contract --target wasm32-unknown-unknown -- -D warnings

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