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/api/escalation_routes.py

@@ -12,7 +12,7 @@ Endpoints:
 """
 
 import logging
-from datetime import datetime
+from datetime import datetime, timezone
 from typing import Optional, Any, Dict
 
 from fastapi import APIRouter, Depends, HTTPException, Query, Header
@@ -244,7 +244,7 @@ async def update_escalation(
 
     set_clauses = ", ".join(f"{k} = :{k}" for k in updates.keys())
     updates["id"] = escalation_id
-    updates["updated_at"] = datetime.utcnow()
+    updates["updated_at"] = datetime.now(timezone.utc)
 
     row = db.execute(
         text(
@@ -277,7 +277,7 @@ async def update_status(
 
     resolved_at = request.resolved_at
     if request.status in ('resolved', 'closed') and resolved_at is None:
-        resolved_at = datetime.utcnow()
+        resolved_at = datetime.now(timezone.utc)
 
     row = db.execute(
         text(
@@ -288,7 +288,7 @@ async def update_status(
         {
             "status": request.status,
             "resolved_at": resolved_at,
-            "updated_at": datetime.utcnow(),
+            "updated_at": datetime.now(timezone.utc),
             "id": escalation_id,
         },
     ).fetchone()