fix(workspace): correct Cargo workspace members list

[MerlinTheWhiz]

Closes #238

Changes made:

• Cargo.toml: normalized workspace members and default-members so vault, revenue_pool, and settlement appear exactly once.
• contracts/vault/src/lib.rs: fixed broken vault logic around storage keys, authorized caller handling, settlement checks, allowlist compatibility methods, event payloads, and deduct/batch-deduct behavior.
• contracts/vault/src/test.rs: updated vault tests/fuzz cases to match the repaired contract behavior and restore passing coverage.
• coverage/cobertura.xml, coverage/tarpaulin-report.html: regenerated coverage reports after validation.

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