Validate resistor input before color encoding

[krotname]

Motivation

• The public ResistorColorCodes2.encodeResistorColors accepted any string ending with " ohms" but did not validate the numeric token, allowing malformed, negative, or non-finite values to cause NumberFormatException or invalid enum indexes and crash the encoder.
• Hardening was needed to keep behavior unchanged for valid kata inputs while rejecting untrusted or malformed values safely.

Description

• Wrap the parsing/encoding flow in encodeResistorColors with a try/catch that returns an empty string for invalid inputs instead of propagating exceptions.
• Add finite and bounds checks in encodeResistorOhms using Double.isFinite(tempValue) and a range check (tempValue < 10 || tempValue > 990_000_000) and throw IllegalArgumentException for values outside the supported 10 ohm to 990M ohm range.
• Update ResistorColorCodes2Test to add regression assertions that encodeResistorColors returns "" for malformed and out-of-range inputs such as "abc ohms", "-1 ohms", and "1e309 ohms".
• Files changed: src/main/java/kyu5/ResistorColorCodes2.java, src/test/java/kyu5/ResistorColorCodes2Test.java.

Testing

• Ran mvn -q -Dtest=kyu5.ResistorColorCodes2Test test and the test class passed.
• Ran full test suite with mvn -q test and the build/tests completed successfully.

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[krotname]

Закрываю как superseded by #116: изменения перенесены в одну проверенную ветку, все review findings учтены; локальный mvn verify прошёл полностью.