feat: bound recovery history and add admin prune

[Dopezapha]

Closes #556

Summary

This PR addresses Issue #556 by introducing an upper bound on retained recovery history records per market and providing an admin-gated prune entrypoint in the Predictify Hybrid Soroban contract. These improvements bound persistent storage growth and prevent high ledger rent costs over time from repeated emergency recovery actions.

Requirements & Solutions Implemented

1. Cap Retained History: Restricted completed recovery records to a hard limit of MAX_RECOVERY_HISTORY_PER_MARKET = 100. History is automatically capped and trimmed when a resolved state is saved.
2. Separate Active & Completed States: Split legacy combined recovery maps into separate active and history maps under recovery_records and recovery_history respectively. An automatic migration (ensure_migrated) was introduced for backward compatibility.
3. Admin-Gated Prune Entrypoint: Added prune_recovery_history exposed in lib.rs and executed via RecoveryStorage::prune_history. It enforces administrative authorization (admin.require_auth()) and restricts batch operations to MAX_RECOVERY_PRUNE_BATCH = 30 for gas safety.
4. Preserve Active State: Active unresolved recovery states are preserved under the active map and are never deleted by pruning actions.

Core Changes

• contracts/predictify-hybrid/src/recovery.rs:
  • Defined bounds configurations (MAX_RECOVERY_HISTORY_PER_MARKET, MAX_RECOVERY_PRUNE_BATCH).
  • Implemented ensure_migrated for seamless backward compatibility.
  • Updated save() to store completed/resolved entries in the bounded history map and unresolved items in the active map.
  • Added the prune_history function containing authority and batch bounds logic.
  • Added comprehensive unit tests covering all required edge cases.
• contracts/predictify-hybrid/src/lib.rs:
  • Exposed prune_recovery_history as a public admin entrypoint.

Verification & Testing

Added isolated unit tests to fully validate functionality:

• test_recovery_history_capped_per_market: Confirms completed history truncates to exactly 100 entries.
• test_prune_preserves_active_recovery: Assures that active unresolved recovery records remain intact after completed history pruning.
• test_prune_count_greater_than_stored: Validates safe degradation when requested prune count exceeds stored history length.
• test_prune_requires_admin: Confirms that unauthorized or non-admin attempts are rejected with Error::Unauthorized.

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