Replace panic on zero polynomial divisor with None

[viktorking7]

Description:

• Summary: Align polynomial division APIs to return None on zero divisor instead of panicking.
• Motivation: Prevent unexpected process crashes and make behavior consistent with Option-returning signatures.
• Changes:
  • poly/src/polynomial/univariate/mod.rs:
    • naive_div: panic! → return None when divisor is zero
    • hensel_div: panic! → return None when divisor is zero
• Impact:
  • Eliminates potential DoS via zero divisor
  • Preserves API semantics; callers using expect(...) retain explicit failure handling