refactor: implement centralized event system, add timelock functionality, and introduce upgrade delay configuration

[Folex1275]

PR Description: Nestera Event System Modernization & Security Infrastructure

Description

This PR implements a comprehensive modernization of the Nestera protocol's event system and integrates mission-critical security infrastructure. The primary goal was to migrate from the deprecated env.events().publish pattern to the type-safe, GAS-efficient #[contractevent] macro system. Additionally, this PR introduces secure contract upgradeability and administrative timelocks to enhance protocol governance.

Closes

Closes #863
Closes #864
Closes #865
Closes #866

Changes

1. Event System Refactor

• Unified Event Enum: Consolidated 14 module-specific event definitions into a single, unified ProtocolEvent enum in contracts/src/events.rs.
• Macro Migration: Successfully migrated all 57 event emission calls to the #[contractevent] pattern.
• Improved Type Safety: Refactored logic to use the unified ProtocolEvent across config, flexi, goal, group, lock, staking, rewards, treasury, and token modules.

2. Security Infrastructure Integration

• Secure Upgrades: Integrated upgrade.rs to allow administrative contract upgrades with mandatory logic checks and version tracking.
• Timelock Mechanism: Implemented timelock.rs, exposing queue and execute functions to enforce a delay (configured via upgrade_delay) on sensitive administrative actions.
• Config Enhancement: Updated initialize_config and the Config struct to support security parameters, including the new upgrade_delay.

3. Code Quality & Stability

• Resolved Macro Panics: Fixed persistent darling macro panics by simplifying the event structure into a single top-level enum.
• Error Handling: Standardized error responses across security modules using SavingsError.
• Cleanup: Removed unused imports and deprecated event definitions across the entire contract suite.

Verification Results

• Logic Integrity: All core protocol logic (deposits, withdrawals, group contributions) remains intact with updated event tracking.
• Event Emission: Verified that functions like create_savings_plan, route_to_strategy, and harvest_strategy correctly emit events via the new enum.
• Security Flow: Validated (via code audit) the schedule -> execute flow for upgrades and timelocked actions.

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Project	Deployment	Actions	Updated (UTC)
nestera	Error		Jun 1, 2026 9:26pm

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