feat(invoice-token): add account freeze controls

[dotmantissa]

Description

I added admin controlled account freeze and unfreeze hooks to the invoice token contract. Frozen accounts are blocked from transfers, delegated transfers, burns, approvals, allowance extensions, and mint participation. The implementation stores frozen state persistently, emits freeze and unfreeze events, exposes a read only status query, and validates repeated state transitions.

Closes #105

Type of Change

• Bug fix (non breaking change which fixes an issue)
• New feature (non breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)
• Documentation update
• UI/UX improvement
• Code refactoring
• Test addition or update
• Configuration change

Checklist

• My code follows the code style of this project
• I have performed a self review of my own code
• I have commented my code, particularly in hard to understand areas
• I have made corresponding changes to the documentation (not applicable to this contract only change)
• My changes generate no new warnings in the affected package
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Testing

How to Test

1. Run cargo fmt --package invoice-token -- --check.
2. Run cargo test --package invoice-token.
3. Run cargo clippy --package invoice-token --all-targets --all-features -- -D warnings and build the release WASM with cargo build --package invoice-token --release --target wasm32v1-none.

Test Coverage

• Unit tests added/updated
• Integration tests added/updated
• E2E tests added/updated (if applicable)
• Manual testing completed

Screenshots (if applicable)

Not applicable.

Additional Notes

The affected invoice-token package passes all scoped checks. Full workspace checks are currently blocked by pre-existing syntax and compilation errors in invoice-escrow and payment-distributor on upstream dev; those unrelated files are unchanged in this PR.

For Reviewers

• Code quality and readability
• Test coverage
• Security implications
• Performance impact
• Breaking changes

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