remove disburse_recurring and related proposal functions to streamlin…

[akprinciple]

closes #447

Summary

This PR resolves the recurring disbursement regression by enforcing strict pre-flight guardrails prior to executing token transfers, ensuring early and safe failure when the contract is frozen or insufficiently funded.

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Changes

• **Deleted duplicated codes
• Freeze State Guard: Injected require_not_frozen at the very beginning of disburse_recurring.
• Pre-Transfer Balance Validation: Added an explicit balance verification step against the contract's token reserves before transferring the period disbursement amount.
• Non-Mutating Failure Mode: Returns Error::TransferFailed immediately when treasury balance is insufficient, preventing any mutations to recurring schedule state.
• Error Contract Preservation: Preserved established contract error semantics for transfer failures across the codebase.
• Source Hygiene & De-duplication: Removed a stale, duplicated code block in lib.rs that was causing duplicate method definitions and compiler collisions in the AccordContract implementation.

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Why This Change

The recurring payout path must fail safely and deterministically under invalid conditions:

• Contract Freeze Protection: Prevents disbursements from proceeding when administrative or emergency freezes are active.
• Treasury Solvency & State Safety: Blocks execution and leaves schedule records intact when the treasury cannot cover the disbursement, avoiding partial or inconsistent state updates.
• Build Integrity: Resolves compiler collisions to maintain a clean build across the contract implementation.

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