Enforce-upgrade-safety-gates-and-migration-validation-in-the-contract…

[Devthopia]

PR Description — Enforce Upgrade-Safety Gates and Migration Validation

Summary

This PR hardens the contract upgrade lifecycle by adding safety gates and migration validation to prevent unsafe upgrades, invariant drift, and repeated or malicious initializer execution.

Changes

• Added validation to block upgrades when safety gates or contract invariants fail.
• Added migration-window checks to prevent upgrades during unsafe migration states.
• Prevented repeated or malicious initializer/re-entry paths while preserving legitimate upgrade flows.
• Added and updated upgrade and guard tests covering failure and edge-case scenarios.
• Updated contract storage, admin, metadata, and lifecycle logic to support upgrade-safety validation.
• Added documentation covering safe deployment, migration, testing, and rollback expectations.

Testing

• Added test coverage for failed upgrade gate checks.
• Added migration safety and invariant validation tests.
• Added tests for repeated initialization and malicious re-entry scenarios.
• Verified that legitimate upgrade flows continue to work as expected.

Closes #554

[MaryammAli]

LGTM