[Logic] Add timestamp tracking to all storage entries

[AbelOsaretin]

Description

None of the storage entries (projects, investments, whitelist) track when they were created or last modified. Timestamps would enable:

• Time-based queries and analytics
• Audit trails
• Time-based business logic (e.g., maturity dates)

Current Code Locations

• project_registry/src/types.rs — ProjectData
• investment_vault/src/types.rs — VaultKey

Recommendation

• Add created_at: u64 and updated_at: u64 fields to ProjectData
• Add timestamp to investment records
• Use env.ledger().timestamp() for consistent timestamps

Severity

Low — Improves auditability and enables time-based features.

[CollinsKRO]

@CollinsKRO has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello maintainer pls assign me this issue. Thanks.

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[miraclesonly]

@miraclesonly has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Please let me work on this

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