[SC-REP-051] Implement profile blacklisting logic for malicious actors

[Trovic1]

Closes #405

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Summary

• implement blacklist-aware reputation profile storage in the Soroban reputation contract
• add custom profile metrics for completed jobs, review aggregates, and active badge levels
• add fixed-point arithmetic for rating averages and decay-based score reductions
• restrict score adjustment and blacklist flows to an authorized contract address
• add contract tests for empty profile loads, badge upgrades, blacklist behavior, and unauthorized review rejection

What Changed

• refactored reputation storage to use structured Profile, RoleMetrics, and ReviewAggregate models
• added blacklist state and public getters exposing blacklist and badge metadata
• updated review submission logic to safely compute average rating basis points
• added admin configuration for an authorized updater contract
• added blacklist and decay logic for malicious actor handling
• expanded unit coverage for security-sensitive reputation flows

Acceptance Criteria Coverage

• reputation profiles load and save correctly without panicking on empty accounts
• badge upgrades trigger and level changes reflect immediately in public getters
• vulnerability tests prove arbitrary direct reviews from unverified public keys are rejected

Testing

• cargo test -p reputation

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[Trovic1]

@soomtochukwu done