Contracts: Consolidate duplicate total_shares and total_assets storage

[Junirezz]

Context

Vault accounting state is split across VaultState (DataKey::State) and legacy scalar keys DataKey::TotalShares, DataKey::TotalAssets, and DataKey::TotalAssets used in deposit/withdraw.

Problem / Gap

deposit updates DataKey::TotalAssets, DataKey::TotalShares, and VaultState fields independently. total_shares() reads from VaultState while some paths read DataKey::TotalShares directly. Divergence risks incorrect share-price math and complicates upgrades.

Proposed approach

• Choose a single source of truth (prefer VaultState) and deprecate redundant keys with a migration helper in upgrade.rs.
• Add invariant tests asserting state.total_shares == sum(ShareBalance) and state.total_assets consistency with idle + strategy value.
• Document storage layout changes in docs/architecture.md.

Files/areas affected

• contracts/vault/src/lib.rs
• contracts/vault/src/upgrade.rs
• contracts/vault/src/test.rs, fuzz_math.rs

[Yasir-TechGuy]

@Yasir-TechGuy has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi Maintainer,

I'd like to work on this issue because consistent vault accounting is critical for correctness, security, and future upgrades. I have experience with Soroban smart contracts, state migrations, invariant testing, and storage design. I'm confident in consolidating the accounting model, implementing a safe migration path, and adding robust tests to prevent state divergence.

Please assign this issue to me.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Yasir-TechGuy to this issue.

[Devsol-01]

@Devsol-01 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Please can i work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Devsol-01 to this issue.

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