fixup(pipeline-hardening M4/M5): purge count, shared toast helper, clean imports

- Fix RabbitMQ purge_queue to report the pre-purge message count instead of
  the post-purge depth (which was always 0).
- Add shared attach_toast helper in admin templating; remove duplicated inline
  _attach_toast implementations in review.py and mq.py.
- Keep purge confirmation case-sensitive so the typed safeguard works as intended.
- Fix test imports to use known-first-party 'contract_check' per isort config.

src/contract_check/api/admin/mq.py

@@ -12,7 +12,7 @@ from fastapi import APIRouter, Depends, Form, HTTPException, Request, status
 from fastapi.responses import HTMLResponse, RedirectResponse
 
 from src.contract_check.api.admin.auth import AdminUser, HtmxGuard, require_admin
-from src.contract_check.api.admin.templating import templates
+from src.contract_check.api.admin.templating import attach_toast, templates
 from src.contract_check.core.logging import get_logger
 from src.contract_check.core.mq.management import (
     MqManagementDisabledError,
@@ -36,12 +36,6 @@ def _client() -> RabbitMQManagementClient:
     return RabbitMQManagementClient()
 
 
-def _attach_toast(response: RedirectResponse, toast: str) -> None:
-    import json
-
-    response.headers["HX-Trigger"] = json.dumps({"showToast": toast})
-
-
 def _safe_toast(toast: str) -> str:
     # Keep toast text short and URL-safe for redirects.
     return toast[:200]
@@ -184,7 +178,7 @@ async def requeue_dlq(
     response = RedirectResponse(
         url=f"/admin/mq/dlq/{queue_name}", status_code=status.HTTP_303_SEE_OTHER
     )
-    _attach_toast(response, toast)
+    attach_toast(response, toast)
     return response
 
 
@@ -221,11 +215,14 @@ async def purge_dlq(
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="unknown DLQ")
 
     expected = f"purge {queue_name}"
-    if confirmation.strip().lower() != expected.lower():
-        return RedirectResponse(
-            url=f"/admin/mq/dlq/{queue_name}/purge/confirm?toast=Неверное+подтверждение.+Введите+%27{expected}%27",
+    if confirmation.strip() != expected:
+        toast = f"Неверное подтверждение. Введите '{expected}'"
+        response = RedirectResponse(
+            url=f"/admin/mq/dlq/{queue_name}/purge/confirm",
             status_code=status.HTTP_303_SEE_OTHER,
         )
+        attach_toast(response, toast)
+        return response
 
     client = _client()
     try:
@@ -252,5 +249,5 @@ async def purge_dlq(
     response = RedirectResponse(
         url=f"/admin/mq/dlq/{queue_name}", status_code=status.HTTP_303_SEE_OTHER
     )
-    _attach_toast(response, toast)
+    attach_toast(response, toast)
     return response

src/contract_check/api/admin/review.py

@@ -7,7 +7,6 @@ All mutations are HTMX-driven and protected by the ``HX-Request`` CSRF guard.
 from __future__ import annotations
 
 import datetime as dt
-import json
 import uuid
 from decimal import Decimal
 from typing import Annotated
@@ -16,7 +15,7 @@ from fastapi import APIRouter, Depends, Form, HTTPException, Request, status
 from fastapi.responses import HTMLResponse, RedirectResponse
 
 from src.contract_check.api.admin.auth import AdminUser, HtmxGuard, require_admin
-from src.contract_check.api.admin.templating import templates
+from src.contract_check.api.admin.templating import attach_toast, templates
 from src.contract_check.api.deps import AsyncSessionDep, PublisherDep
 from src.contract_check.core.config import get_settings
 from src.contract_check.core.db.repositories import ReviewQueueRepository
@@ -124,7 +123,7 @@ async def list_review_queue(
             "conf_max": conf_max,
         },
     )
-    _attach_toast(response, request.query_params.get("toast"))
+    attach_toast(response, request.query_params.get("toast"))
     return response
 
 
@@ -150,15 +149,10 @@ async def review_detail(
             "toast": request.query_params.get("toast"),
         },
     )
-    _attach_toast(response, request.query_params.get("toast"))
+    attach_toast(response, request.query_params.get("toast"))
     return response
 
 
-def _attach_toast(response: HTMLResponse, toast: str | None) -> None:
-    if toast:
-        response.headers["HX-Trigger"] = json.dumps({"showToast": toast})
-
-
 def _review_action_redirect(
     *,
     document_id: uuid.UUID,

src/contract_check/api/admin/templating.py

@@ -8,8 +8,10 @@ datetime rendering consistent.
 from __future__ import annotations
 
 import datetime as dt
+import json
 from pathlib import Path
 
+from fastapi import Response
 from fastapi.templating import Jinja2Templates
 
 _TEMPLATES_DIR = Path(__file__).resolve().parent / "templates"
@@ -33,5 +35,11 @@ def _yes_no_none(value: object) -> str:
     return "—"
 
 
+def attach_toast(response: Response, toast: str | None) -> None:
+    """Attach an HTMX toast trigger to any response that supports headers."""
+    if toast:
+        response.headers["HX-Trigger"] = json.dumps({"showToast": toast})
+
+
 templates.env.filters["dt"] = _format_dt
 templates.env.filters["yn"] = _yes_no_none

src/contract_check/core/mq/management.py

@@ -240,6 +240,9 @@ class RabbitMQManagementClient:
         """Empty a queue and return the number of messages removed."""
         self._ensure_enabled()
         url = f"/api/queues/{self._vhost}/{quote(queue_name, safe='')}/contents"
+        # Capture the pre-purge depth so we can report how many were removed.
+        before_info = await self.get_queue_info(queue_name)
+        messages_before = max(0, before_info.messages)
         try:
             resp = await self.client.delete(url)
         except httpx.NetworkError as exc:
@@ -254,9 +257,7 @@ class RabbitMQManagementClient:
                 status_code=resp.status_code,
                 body=resp.text[:500],
             )
-        # Successful purge returns no body; the queue is now empty.
-        info = await self.get_queue_info(queue_name)
-        return PurgeResult(messages_removed=max(0, info.messages))
+        return PurgeResult(messages_removed=messages_before)
 
     async def requeue_batch(
         self,

tests/unit/test_mq_management.py

@@ -12,7 +12,7 @@ import httpx
 import pytest
 import respx
 
-from src.contract_check.core.mq.management import (
+from contract_check.core.mq.management import (
     MqManagementDisabledError,
     MqManagementNotFoundError,
     MqManagementResponseError,
@@ -23,7 +23,7 @@ from src.contract_check.core.mq.management import (
     RabbitMQManagementClient,
     RequeueResult,
 )
-from src.contract_check.core.mq.topology import DLQ_FOR
+from contract_check.core.mq.topology import DLQ_FOR
 
 
 @pytest.fixture
@@ -132,18 +132,18 @@ async def test_peek_messages_empty_non_list(mgmt_client: RabbitMQManagementClien
 
 
 @pytest.mark.anyio
-async def test_purge_queue(mgmt_client: RabbitMQManagementClient) -> None:
+async def test_purge_queue_reports_pre_purge_count(mgmt_client: RabbitMQManagementClient) -> None:
     with respx.mock:
         respx.delete("http://rabbitmq:15672/api/queues/%2F/extract.dlq/contents").mock(
             return_value=httpx.Response(204)
         )
         respx.get("http://rabbitmq:15672/api/queues/%2F/extract.dlq").mock(
             return_value=httpx.Response(
-                200, json={"name": "extract.dlq", "messages": 0, "state": "running"}
+                200, json={"name": "extract.dlq", "messages": 3, "state": "running"}
             )
         )
         await mgmt_client.connect()
-        assert await mgmt_client.purge_queue("extract.dlq") == PurgeResult(messages_removed=0)
+        assert await mgmt_client.purge_queue("extract.dlq") == PurgeResult(messages_removed=3)
         await mgmt_client.aclose()