feat: Support fixed-length Array<T, N> property type

[zhanglei1949]

Summary

• Add native fixed-length array property type (INT32[3], DOUBLE[128], etc.) for vertices and edges
• Implement ArrayColumn storage backed by a flat child column for efficient columnar access
• Wire through the full query pipeline: type system, schema, compiler, execution values, serialization, and Python bindings

Closes #506

Changes

• Type system: DataTypeId::kArray, DataType::Array(), ArrayType helpers, ArrayExtraTypeInfo
• Storage: New ArrayColumn class — row i, element j stored at child[i*N + j]
• Execution: Value::ARRAY, ArrayValue, comparison operators for arrays
• Compiler: gopt type conversion, vector cast functions updated
• Serialization: protobuf and YAML schema support for array types
• Python: Array values returned as Python lists via existing bindings
• Tests: Integration tests covering INT32, INT64, FLOAT, DOUBLE arrays; create, query, update operations

Test plan

• python3 -m pytest tests/test_db_array.py — array create, query, update, multi-row
• Existing test suite passes (no regressions to list/struct handling)
• Schema round-trip: create DB with array properties, close, reopen, query

🤖 Generated with Claude Code