Refactor PrimeFactorization: Miller-Rabin, simplify, add tests

[williamfiset]

Summary

• Replace trial-division isPrime (O(√n)) with deterministic Miller-Rabin (O(k log²n)), using 12 witnesses correct for all long values
• Replace PriorityQueue-based loop with simple recursive factor method
• Add overflow-safe mulMod and powMod for modular arithmetic on large values
• Use mulMod in Pollard's rho to avoid overflow on large inputs
• Add Javadoc, apply single-line body formatting rule
• Time complexity is now truly O(n^(1/4)) expected per factor found
• Add 11 JUnit 5 tests: small primes, prime powers, composites, large prime, large semiprime, product verification, edge cases

Test plan

• bazel test //src/test/java/com/williamfiset/algorithms/math:PrimeFactorizationTest — 11 tests pass

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