feat: extract pure fiscal core from sowai-auto (parity-preserving copy)

Copies the 6 pure fiscal modules (domains, chave_acesso, tpag, presets,
resolver, xml_builder) from sowai-auto's backend/app/modules/fiscal/ into
this standalone lib, with only the two mechanical changes required to drop
the app.* dependency: import prefix rename, and TaxRule (ORM) -> TaxRuleLike
(structural Protocol) in the resolver. No other line changes -- byte-level
parity with the auto is the point.

Ports the pure test suites (domains, chave_acesso, resolver with a local
FakeTaxRule satisfying TaxRuleLike, xml_builder) plus a new test_presets_data
covering the PRESETS dict directly (the auto's equivalent test exercises the
apply-preset HTTP/DB flow, which isn't part of the extracted pure core).

55 tests pass locally via `uv run pytest`, no Postgres/k8s required.

tests/test_presets_data.py

@@ -0,0 +1,69 @@
+"""Presets fiscais seed-editáveis: teste PURO do dict `PRESETS` (dados,
+não a API `/tax-profiles/apply-preset/*` -- aquela é do produto, DB/HTTP,
+não faz parte do núcleo puro extraído). Os valores REAIS vieram do iCode
+da Thiago (perfis "Padrão" cód 110 e "Óleos/ST" cód 108) -- estes testes
+travam o contrato de dados que o consumidor (auto) usa para semear
+`TaxRule`/`TaxProfile`."""
+from decimal import Decimal
+
+from sowai_fiscal.presets import PRESETS, FiscalPreset, PresetRule
+
+
+def test_presets_catalog_has_the_two_icode_profiles():
+    assert {"autopecas_simples_padrao", "autopecas_simples_st"} <= PRESETS.keys()
+
+
+def test_padrao_preset_has_venda_and_devolucao_icms_rules():
+    preset = PRESETS["autopecas_simples_padrao"]
+    assert isinstance(preset, FiscalPreset)
+    assert preset.regime_alvo == "1"
+
+    icms_rules = [r for r in preset.rules if r.tax_domain == "icms"]
+    assert len(icms_rules) == 2
+
+    venda = next(r for r in icms_rules if r.tipo_operacao == "venda")
+    assert venda.csosn == "102"
+    assert venda.cfop == "5102"
+    assert venda.aliquota == Decimal("0")
+
+    devolucao = next(r for r in icms_rules if r.tipo_operacao == "devolucao")
+    assert devolucao.csosn == "102"
+    assert devolucao.cfop == "1202"
+
+
+def test_padrao_preset_pis_cofins_cst_08():
+    preset = PRESETS["autopecas_simples_padrao"]
+    pis = next(r for r in preset.rules if r.tax_domain == "pis")
+    cofins = next(r for r in preset.rules if r.tax_domain == "cofins")
+    assert pis.cst == "08"
+    assert cofins.cst == "08"
+    assert pis.aliquota == Decimal("0")
+    assert cofins.aliquota == Decimal("0")
+
+
+def test_st_preset_has_venda_and_devolucao_icmsst_rules():
+    preset = PRESETS["autopecas_simples_st"]
+    icmsst_rules = [r for r in preset.rules if r.tax_domain == "icmsst"]
+    assert len(icmsst_rules) == 2
+
+    venda = next(r for r in icmsst_rules if r.tipo_operacao == "venda")
+    assert venda.csosn == "500"
+    assert venda.cfop == "5405"
+
+    devolucao = next(r for r in icmsst_rules if r.tipo_operacao == "devolucao")
+    assert devolucao.csosn == "500"
+    assert devolucao.cfop == "1202"
+
+
+def test_st_preset_pis_cofins_cst_04_monofasico():
+    preset = PRESETS["autopecas_simples_st"]
+    pis = next(r for r in preset.rules if r.tax_domain == "pis")
+    cofins = next(r for r in preset.rules if r.tax_domain == "cofins")
+    assert pis.cst == "04"
+    assert cofins.cst == "04"
+
+
+def test_no_preset_rule_carries_origem():
+    # NENHUM preset carrega `origem`: origem é sempre do Part (review do
+    # frontend, 2026-07-14) -- `PresetRule` não tem sequer o campo.
+    assert not hasattr(PresetRule(tax_domain="icms"), "origem")