feat: implement decentralized storage applications for proof data persistence (#399)

[gbengaeben]

Summary

Implements decentralized storage applications for proof data persistence as specified in #399.

Backend Changes

• DataPersistence.ts - Proof data persistence with deduplication, automatic retry logic, and auto-backup
• DistributedStorage.ts - Distributed file storage across network nodes with incentive mechanisms for storage providers
• IntegrityVerifier.ts - Blockchain-verified storage integrity with Merkle proofs, hash-chain proofs, and ZKP support
• StorageApplications.ts - Main orchestration class tying all storage subsystems together
• StorageApplicationService.ts - Service layer with singleton lifecycle management

Frontend Changes

• PersistencePanel.tsx - Interactive dashboard for viewing, persisting, and verifying proof data with efficiency metrics
• DistributedStorage.tsx - Full dashboard with tabs for nodes, distributions, and incentive tracking

Acceptance Criteria

• ✅ GIVEN storage application, WHEN used, THEN proof data is stored persistently
• ✅ GIVEN distributed storage, WHEN implemented, THEN data is available across network nodes
• ✅ GIVEN blockchain verification, WHEN applied, THEN storage integrity is cryptographically proven
• ✅ GIVEN incentive mechanisms, WHEN active, THEN storage providers are rewarded
• ✅ GIVEN efficiency optimization, WHEN applied, THEN storage operations are fast

Closes #399