🧹 Refactor code health: extract resolve_latest_tag_by_strategy

[ffalcinelli]

🎯 What: Extracted the complex semver tag resolution logic out of Resolver::resolve_upgrade and Resolver::get_upgrade_candidate (which originated from the legacy operations.rs) into a separate helper function called resolve_latest_tag_by_strategy.
💡 Why: The complex inline strategy matching logic for major, minor, and latest versions was duplicated across resolve_upgrade and get_upgrade_candidate. Extracting it into a reusable helper function keeps the code DRY, improves readability, and makes the logic easier to test and maintain.
✅ Verification: Verified that the changes successfully compile with cargo check and confirmed that no functionality was broken by running the full cargo test suite.
✨ Result: Improved maintainability and reduced code duplication in the resolver logic.

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PR created automatically by Jules for task 8429771229329959585 started by @ffalcinelli

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.11%. Comparing base (ed6815a) to head (98072a5).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #69   +/-   ##
=======================================
  Coverage   87.11%   87.11%           
=======================================
  Files          28       28           
  Lines        2568     2568           
=======================================
  Hits         2237     2237           
  Misses        331      331           

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