feat: enhance risk scoring with git mining, coverage parsing, and jules rules

[google-labs-jules]

This PR implements Phase 1 of the Risk Scoring Engine Enhancement.
It introduces:

1. GitMiner: A module to analyze git history for file churn and author diversity metrics.
2. CoverageParser: A module to parse test coverage reports from various formats (Cobertura, JaCoCo, Go).
3. Enhanced RiskScorer: Updates the risk scoring logic to use a weighted formula combining static complexity, git churn, test coverage, author diversity, and file size.
4. Jules Rules: A set of static analysis rules specifically designed to detect common issues in LLM-generated code (e.g., empty exception handlers, magic numbers).
5. CLI Integration: Updates the scan command to accept git repo paths and coverage reports, and to apply the new scoring and rules.

Verified with unit tests and integration tests.

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PR created automatically by Jules for task 2293089115775420705 started by @turtacn

[google-labs-jules]

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