refactor(tests): compress admin_client + mock_send_email into conftest

Lift admin_client fixture from 7 duplicate definitions into conftest.py.
Add mock_send_email fixture, replacing 60 inline patch() blocks across
test_emails.py, test_waitlist.py, and test_businessplan.py. Net -197 lines.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/tests/test_waitlist.py

@@ -188,59 +188,55 @@ class TestWorkerTask:
     """Test send_waitlist_confirmation worker task."""
 
     @pytest.mark.asyncio
-    async def test_sends_entrepreneur_confirmation(self):
+    async def test_sends_entrepreneur_confirmation(self, mock_send_email):
         """Task sends confirmation email for entrepreneur signup."""
-        with patch("padelnomics.worker.send_email", new_callable=AsyncMock) as mock_send:
-            await handle_send_waitlist_confirmation({
-                "email": "entrepreneur@example.com",
-                "intent": "signup",
-            })
+        await handle_send_waitlist_confirmation({
+            "email": "entrepreneur@example.com",
+            "intent": "signup",
+        })
 
-            mock_send.assert_called_once()
-            call_args = mock_send.call_args
-            assert call_args.kwargs["to"] == "entrepreneur@example.com"
-            assert "notify you at launch" in call_args.kwargs["subject"].lower()
-            assert "waitlist" in call_args.kwargs["html"].lower()
+        mock_send_email.assert_called_once()
+        call_args = mock_send_email.call_args
+        assert call_args.kwargs["to"] == "entrepreneur@example.com"
+        assert "notify you at launch" in call_args.kwargs["subject"].lower()
+        assert "waitlist" in call_args.kwargs["html"].lower()
 
     @pytest.mark.asyncio
-    async def test_sends_supplier_confirmation(self):
+    async def test_sends_supplier_confirmation(self, mock_send_email):
         """Task sends confirmation email for supplier signup."""
-        with patch("padelnomics.worker.send_email", new_callable=AsyncMock) as mock_send:
-            await handle_send_waitlist_confirmation({
-                "email": "supplier@example.com",
-                "intent": "supplier_growth",
-            })
+        await handle_send_waitlist_confirmation({
+            "email": "supplier@example.com",
+            "intent": "supplier_growth",
+        })
 
-            mock_send.assert_called_once()
-            call_args = mock_send.call_args
-            assert call_args.kwargs["to"] == "supplier@example.com"
-            assert "growth" in call_args.kwargs["subject"].lower()
-            assert "supplier" in call_args.kwargs["html"].lower()
+        mock_send_email.assert_called_once()
+        call_args = mock_send_email.call_args
+        assert call_args.kwargs["to"] == "supplier@example.com"
+        assert "growth" in call_args.kwargs["subject"].lower()
+        assert "supplier" in call_args.kwargs["html"].lower()
 
     @pytest.mark.asyncio
-    async def test_supplier_email_includes_plan_name(self):
+    async def test_supplier_email_includes_plan_name(self, mock_send_email):
         """Supplier confirmation should mention the specific plan."""
-        with patch("padelnomics.worker.send_email", new_callable=AsyncMock) as mock_send:
-            await handle_send_waitlist_confirmation({
-                "email": "supplier@example.com",
-                "intent": "supplier_pro",
-            })
+        await handle_send_waitlist_confirmation({
+            "email": "supplier@example.com",
+            "intent": "supplier_pro",
+        })
 
-            call_args = mock_send.call_args
-            html = call_args.kwargs["html"]
-            assert "pro" in html.lower()
+        call_args = mock_send_email.call_args
+        html = call_args.kwargs["html"]
+        assert "pro" in html.lower()
 
     @pytest.mark.asyncio
-    async def test_uses_transactional_email_address(self):
+    async def test_uses_transactional_email_address(self, mock_send_email):
         """Task should use transactional sender address."""
-        with patch("padelnomics.worker.send_email", new_callable=AsyncMock) as mock_send:
-            await handle_send_waitlist_confirmation({
-                "email": "test@example.com",
-                "intent": "signup",
-            })
+        await handle_send_waitlist_confirmation({
+            "email": "test@example.com",
+            "intent": "signup",
+        })
 
-            call_args = mock_send.call_args
-            assert call_args.kwargs["from_addr"] == core.EMAIL_ADDRESSES["transactional"]
+        call_args = mock_send_email.call_args
+        assert call_args.kwargs["from_addr"] == core.EMAIL_ADDRESSES["transactional"]
 
 
 # ── TestAuthRoutes ────────────────────────────────────────────────