Fix: Inconsistent Error Messages.

[Lansa-18]

Closes #103

Error Message Standardization

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Bug Fixes

• OracleError::BatchSizeExceeded — replaced hardcoded literal 4012 with named constant oracle_codes::ORACLE_BATCH_SIZE_EXCEEDED
• compliance_registry::Error — fixed 8 error variants that were mapped to wrong or duplicate codes (e.g. HighRisk, ProhibitedJurisdiction, InvalidRiskScore, and JurisdictionNotSupported all incorrectly shared COMPLIANCE_CHECK_FAILED)

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New Infrastructure

Addition	Description
ErrorMessage struct	Standardized snapshot combining code, category, message, description, and i18n_key into a single type
ContractError::error_i18n_key()	New default trait method returning a "category.variant" dot-notation key (e.g. "compliance.not_verified")
ContractError::to_error_message()	New default trait method that builds an ErrorMessage from any error, zero allocation
i18n.rs module	New localization module with SupportedLocale, LocalizedMessage, lookup(), and lookup_default() using static match-based lookup (fully no_std compatible)

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New Constants

• oracle_codes::ORACLE_BATCH_SIZE_EXCEEDED = 4012
• 8 new compliance_codes constants: COMPLIANCE_HIGH_RISK through COMPLIANCE_DATA_RETENTION_EXPIRED (6006–6013)

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Localization Keys

All 38 keys implemented across four categories:

common.* · oracle.* · compliance.* · monitoring.*

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Tests

9 unit tests covering:

• Unique compliance codes
• i18n key correctness
• to_error_message() field population
• Known/unknown key lookup
• lookup_default() consistency

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[Lansa-18]

@LaGodxy Kindly go through chief.