[nth-bailey]

Summary

As discussed in #191, this PR migrates Badger's XML data-binding generation and deserialization stack:

1. xsdata -> pyxsdata>=1.6.1 with --lazy-load: Generates strongly-typed Python @dataclass models utilizing PEP 562 module attribute lazy loading.
2. Instantaneous Startup: Replaces the eager domain/netex/__init__.py re-export (which previously loaded ~11,000 classes into memory upon any domain.netex import) with on-demand PEP 562 resolution.
3. PolyXML Acceleration: Integrates polyxml (native Rust core powered by quick-xml + lexical-core) into MyXmlSerializer.unmarshall, providing native C-speed XML unmarshalling directly into the generated dataclasses, with seamless fallback to pyxsdata.formats.dataclass.parsers.XmlParser.

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Benchmarks

1. Package Startup / Import Latency

Operation	Before (xsdata eager)	After (pyxsdata + PEP 562 lazy)	Speedup
import domain.netex	5,418.68 ms	5.56 ms	~974x faster

Eliminates the ~5.4-second freeze whenever any CLI tool, transformer, or module imports domain.netex.

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2. XML Deserialization Throughput (5,000 ScheduledStopPoint Objects)

Engine	Total Time (5k items)	Throughput	Relative Performance
XmlParser (pure Python / lxml)	344.1 ms	14,531 ops/sec	1.0x (baseline)
PolyXML (Native Rust)	71.4 ms	70,071 ops/sec	4.8x faster

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Verification & Test Results

All 28 unit tests pass cleanly:

Ran 28 tests in 10.892s

OK