fix: v1 BaseController.to_json serialization error

[simontaurus]

Fixes #20

v1 BaseController.to_json() failed when controller fields contained non-serializable objects (e.g. LocalDatabaseDriver). Now uses _raw_dict() to strip controller-only fields before serialization, matching the v2 behavior.

[github-actions]

📊 Benchmark Results

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📊 Benchmark Comparison (threshold: 1.3x)
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➖ Unchanged (within threshold):
  ➖ test_simple_dict_document_store: 0.0015s → 0.0015s (-0.7%)
  ➖ test_sqlite_document_store: 0.0017s → 0.0018s (+5.6%)
  ➖ test_local_sparql_store: 0.0446s → 0.0365s (-18.2%)
  ➖ test_oneof_subschema: 0.0557s → 0.0520s (-6.5%)
  ➖ test_enum_docstrings: 0.0458s → 0.0464s (+1.3%)
  ➖ test_subclass_inheritance: 0.0447s → 0.0463s (+3.6%)
  ➖ test_class_hierarchy: 0.0434s → 0.0471s (+8.6%)
  ➖ test_core[v1]: 0.0371s → 0.0365s (-1.5%)
  ➖ test_core[v2]: 0.0434s → 0.0401s (-7.4%)
  ➖ test_schema_generation[v1]: 0.0016s → 0.0016s (+0.2%)
  ➖ test_schema_generation[v2]: 0.0028s → 0.0033s (+15.7%)
  ➖ test_simple_json: 0.0007s → 0.0007s (+0.1%)
  ➖ test_complex_graph: 0.0015s → 0.0015s (-0.2%)

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Summary: 0 regressions, 0 improvements, 13 unchanged
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✅ No significant performance regressions

Threshold: 1.3x (30% slower triggers a regression warning)

Note: Benchmarks are informational only and won't fail the build.

_{💡 Tip: Download the benchmark-results artifact for detailed JSON data}