refactor: phase 0 guardrails + phase 1 step 2 (models.py split)

Squash of branch refactor/phase0-guardrails-and-models-split — 4 commits,
81 files, 173/173 pytest green, OpenAPI contract preserved (360 paths /
484 operations).

## Phase 0 — Architecture guardrails

Three defense-in-depth layers to keep the architecture rules enforced
regardless of who opens Claude Code in this repo:

  1. .claude/settings.json PreToolUse hook on Write/Edit blocks any file
     that would exceed the 500-line hard cap. Auto-loads in every Claude
     session in this repo.
  2. scripts/githooks/pre-commit (install via scripts/install-hooks.sh)
     enforces the LOC cap locally, freezes migrations/ without
     [migration-approved], and protects guardrail files without
     [guardrail-change].
  3. .gitea/workflows/ci.yaml gains loc-budget + guardrail-integrity +
     sbom-scan (syft+grype) jobs, adds mypy --strict for the new Python
     packages (compliance/{services,repositories,domain,schemas}), and
     tsc --noEmit for admin-compliance + developer-portal.

Per-language conventions documented in AGENTS.python.md, AGENTS.go.md,
AGENTS.typescript.md at the repo root — layering, tooling, and explicit
"what you may NOT do" lists. Root CLAUDE.md is prepended with the six
non-negotiable rules. Each of the 10 services gets a README.md.

scripts/check-loc.sh enforces soft 300 / hard 500 and surfaces the
current baseline of 205 hard + 161 soft violations so Phases 1-4 can
drain it incrementally. CI gates only CHANGED files in PRs so the
legacy baseline does not block unrelated work.

## Deprecation sweep

47 files. Pydantic V1 regex= -> pattern= (2 sites), class Config ->
ConfigDict in source_policy_router.py (schemas.py intentionally skipped;
it is the Phase 1 Step 3 split target). datetime.utcnow() ->
datetime.now(timezone.utc) everywhere including SQLAlchemy default=
callables. All DB columns already declare timezone=True, so this is a
latent-bug fix at the Python side, not a schema change.

DeprecationWarning count dropped from 158 to 35.

## Phase 1 Step 1 — Contract test harness

tests/contracts/test_openapi_baseline.py diffs the live FastAPI /openapi.json
against tests/contracts/openapi.baseline.json on every test run. Fails on
removed paths, removed status codes, or new required request body fields.
Regenerate only via tests/contracts/regenerate_baseline.py after a
consumer-updated contract change. This is the safety harness for all
subsequent refactor commits.

## Phase 1 Step 2 — models.py split (1466 -> 85 LOC shim)

compliance/db/models.py is decomposed into seven sibling aggregate modules
following the existing repo pattern (dsr_models.py, vvt_models.py, ...):

  regulation_models.py       (134) — Regulation, Requirement
  control_models.py          (279) — Control, Mapping, Evidence, Risk
  ai_system_models.py        (141) — AISystem, AuditExport
  service_module_models.py   (176) — ServiceModule, ModuleRegulation, ModuleRisk
  audit_session_models.py    (177) — AuditSession, AuditSignOff
  isms_governance_models.py  (323) — ISMSScope, Context, Policy, Objective, SoA
  isms_audit_models.py       (468) — Finding, CAPA, MgmtReview, InternalAudit,
                                     AuditTrail, Readiness

models.py becomes an 85-line re-export shim in dependency order so
existing imports continue to work unchanged. Schema is byte-identical:
__tablename__, column definitions, relationship strings, back_populates,
cascade directives all preserved.

All new sibling files are under the 500-line hard cap; largest is
isms_audit_models.py at 468. No file in compliance/db/ now exceeds
the hard cap.

## Phase 1 Step 3 — infrastructure only

backend-compliance/compliance/{schemas,domain,repositories}/ packages
are created as landing zones with docstrings. compliance/domain/
exports DomainError / NotFoundError / ConflictError / ValidationError /
PermissionError — the base classes services will use to raise
domain-level errors instead of HTTPException.

PHASE1_RUNBOOK.md at backend-compliance/PHASE1_RUNBOOK.md documents
the nine-step execution plan for Phase 1: snapshot baseline,
characterization tests, split models.py (this commit), split schemas.py
(next), extract services, extract repositories, mypy --strict, coverage.

## Verification

  backend-compliance/.venv-phase1: uv python install 3.12 + pip -r requirements.txt
  PYTHONPATH=. pytest compliance/tests/ tests/contracts/
  -> 173 passed, 0 failed, 35 warnings, OpenAPI 360/484 unchanged

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend-compliance/compliance/services/auto_risk_updater.py

@@ -11,7 +11,7 @@ Sprint 6: CI/CD Evidence Collection (2026-01-18)
 """
 
 import logging
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Dict, List, Optional
 from dataclasses import dataclass
 from enum import Enum
@@ -140,7 +140,7 @@ class AutoRiskUpdater:
         if new_status != old_status:
             control.status = ControlStatusEnum(new_status)
             control.status_notes = self._generate_status_notes(scan_result)
-            control.updated_at = datetime.utcnow()
+            control.updated_at = datetime.now(timezone.utc)
             control_updated = True
             logger.info(f"Control {scan_result.control_id} status changed: {old_status} -> {new_status}")
 
@@ -225,7 +225,7 @@ class AutoRiskUpdater:
             source="ci_pipeline",
             ci_job_id=scan_result.ci_job_id,
             status=EvidenceStatusEnum.VALID,
-            valid_from=datetime.utcnow(),
+            valid_from=datetime.now(timezone.utc),
             collected_at=scan_result.timestamp,
         )
 
@@ -298,8 +298,8 @@ class AutoRiskUpdater:
                         risk_updated = True
 
             if risk_updated:
-                risk.last_assessed_at = datetime.utcnow()
-                risk.updated_at = datetime.utcnow()
+                risk.last_assessed_at = datetime.now(timezone.utc)
+                risk.updated_at = datetime.now(timezone.utc)
                 affected_risks.append(risk.risk_id)
                 logger.info(f"Updated risk {risk.risk_id} due to control {control.control_id} status change")
 
@@ -354,7 +354,7 @@ class AutoRiskUpdater:
         try:
             ts = datetime.fromisoformat(timestamp.replace('Z', '+00:00'))
         except (ValueError, AttributeError):
-            ts = datetime.utcnow()
+            ts = datetime.now(timezone.utc)
 
         # Determine scan type from evidence_type
         scan_type = ScanType.SAST  # Default