feat: add MurmurHash2 hash() and unit+integration tests

[Fengzdadi]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

• Closes feat: hash gen #355

Description:

• Add a new murmur_hash function (MurmurHash2 64-bit variant) under nebula3/utils/hash.py
• Remove ctypes dependency and use int.from_bytes for better performance and readability
• Support both str (UTF-8) and bytes inputs, with appropriate type checking
• Add comprehensive unit tests (tests/test_hash.py) covering:
  • Empty input, single byte, exactly 8 bytes, >8 bytes, Unicode strings
  • Seed variation, idempotency, invalid types, large inputs
• Add integration tests (tests/test_hash_integration.py) to verify client hash() against server YIELD hash(...)

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[wey-gu]

looks like our runner's pdm env is dirty, trying to run py310's pdm code on py37, where there are walrus symbol := that's foreign to py37.