feat(contracts): add fuzz testing, gas optimization, multisig, and storage optimization

[Shredder401k]

Summary

Implements four critical contract enhancements for the Nestera Soroban smart contract: multi-signature admin control, storage optimization, gas optimization, and comprehensive fuzz testing infrastructure.

Changes

#867 Multi-Signature Admin Control

• Added contracts/src/multisig.rs with complete multi-sig proposal system
• Implemented configurable threshold (minimum 2 signers required)
• Added signature collection and verification
• Created proposal lifecycle: create → sign → execute
• Supported actions: SetAdmin, SetTreasury, Upgrade, Pause/Unpause, Rate changes
• MultiSigConfig, MultiSigProposal, MultiSigAction structs with storage keys
• Signer approval tracking to prevent duplicate signatures

#868 Contract Storage Optimization

• Added contracts/src/storage_optimization.rs with efficient data packing
• PackedUserData: packs user data into compact struct (savings_count as u16, flags as u8)
• CompactSavingsPlan: optimizes storage with u32/u16 types instead of u64 where safe
• StoragePacker: batch read/write operations to reduce storage calls
• AddressMap: efficient address-to-value mapping with key packing
• BatchStorage: tracks reads/writes for optimization measurement
• StorageStats: storage usage estimation utilities

#869 Gas Optimization

• Added contracts/src/gas_optimization.rs with optimization utilities
• MemoMap: cache repeated calculations to avoid recomputation
• StorageCache: cache frequently accessed storage values
• LazyValue: defer expensive computations until needed
• BatchProcessor: batch operations to reduce per-item overhead
• Binary search for sorted data lookups
• Inline functions for hot paths (min/max/clamp operations)
• GasEstimator: profile and estimate gas consumption

#870 Comprehensive Fuzz Testing

• Added contracts/src/fuzz_tests.rs with property-based testing framework
• Fuzzer: deterministic PRNG for reproducible test cases
• Arithmetic property tests: overflow/underflow boundary testing
• Access control tests: unauthorized access prevention
• State transition tests: invalid state detection
• Calculation edge cases: zero amounts, precision, time overflow
• Input validation: negative amounts, max values

Testing

• Fuzz tests include deterministic PRNG for reproducible results
• Property-based tests verify arithmetic, state, and access invariants
• All new modules integrated into lib.rs

Closes #867
Closes #868
Closes #869
Closes #870

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Project	Deployment	Actions	Updated (UTC)
nestera	Error		Jun 1, 2026 9:29pm

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