refactor(backend/api): extract Email Template services (Step 4 — file 10 of 18)

compliance/api/email_template_routes.py (823 LOC) -> 295 LOC thin routes
+ 402-line EmailTemplateService + 241-line EmailTemplateVersionService +
61-line schemas file.

Two-service split along natural responsibility seam:

  email_template_service.py (402 LOC):
    - Template type catalog (TEMPLATE_TYPES constant)
    - Template CRUD (list, create, get)
    - Stats, settings, send logs, initialization, default content
    - Shared _template_to_dict / _version_to_dict / _render_template helpers

  email_template_version_service.py (241 LOC):
    - Version CRUD (create, list, get, update)
    - Workflow transitions (submit, approve, reject, publish)
    - Preview and test-send

TEMPLATE_TYPES, VALID_CATEGORIES, VALID_STATUSES re-exported from the
route module for any legacy consumers.

State-transition errors use ValidationError (-> HTTPException 400) to
preserve the original handler's 400 status for "Only draft/review
versions can be ..." checks, since the existing TestClient integration
tests (47 tests) assert status_code == 400.

Verified:
  - 47/47 tests/test_email_template_routes.py pass
  - OpenAPI 360/484 unchanged
  - mypy compliance/ -> Success on 138 source files
  - email_template_routes.py 823 -> 295 LOC
  - Hard-cap violations: 9 -> 8

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

backend-compliance/compliance/schemas/email_template.py

@@ -0,0 +1,62 @@
+"""
+Email template request schemas.
+
+Phase 1 Step 4: extracted from ``compliance.api.email_template_routes``.
+"""
+
+from typing import Optional
+
+from pydantic import BaseModel
+
+
+class TemplateCreate(BaseModel):
+    template_type: str
+    name: Optional[str] = None
+    description: Optional[str] = None
+    category: Optional[str] = None
+    is_active: bool = True
+
+
+class VersionCreate(BaseModel):
+    version: str = "1.0"
+    language: str = "de"
+    subject: str
+    body_html: str
+    body_text: Optional[str] = None
+
+
+class VersionUpdate(BaseModel):
+    subject: Optional[str] = None
+    body_html: Optional[str] = None
+    body_text: Optional[str] = None
+
+
+class PreviewRequest(BaseModel):
+    variables: Optional[dict[str, str]] = None
+
+
+class SendTestRequest(BaseModel):
+    recipient: str
+    variables: Optional[dict[str, str]] = None
+
+
+class SettingsUpdate(BaseModel):
+    sender_name: Optional[str] = None
+    sender_email: Optional[str] = None
+    reply_to: Optional[str] = None
+    logo_url: Optional[str] = None
+    primary_color: Optional[str] = None
+    secondary_color: Optional[str] = None
+    footer_text: Optional[str] = None
+    company_name: Optional[str] = None
+    company_address: Optional[str] = None
+
+
+__all__ = [
+    "TemplateCreate",
+    "VersionCreate",
+    "VersionUpdate",
+    "PreviewRequest",
+    "SendTestRequest",
+    "SettingsUpdate",
+]