feat: real ERPNext Healthcare integration + setup tooling

- Replace all mock tools with real ERPNext Healthcare operations
- ERPNextHealthcare class: patients, practitioners, appointments, schedules
- check_availability queries real practitioner schedules from ERPNext
- create_appointment finds/creates patient + validates conflicts + books in ERPNext
- Add /api/v1/config/test endpoint to validate all service connections
- Add scripts/validate_setup.py for CLI validation of Meta/OpenAI/ERPNext/DB
- Add scripts/seed_knowledge.py with full SKEEN catalog (services, products, packages, FAQ)
- Add tests for webhook, health, and WhatsApp client
- Update main.py to include config router

tests/test_whatsapp_client.py

@@ -0,0 +1,61 @@
+"""Tests for WhatsApp API client."""
+
+import pytest
+import respx
+from httpx import Response
+
+from src.infrastructure.whatsapp.client import WhatsAppClient
+
+
+class TestWhatsAppClient:
+    """Test Meta WhatsApp Business API client."""
+
+    @pytest.fixture
+    def client(self):
+        return WhatsAppClient()
+
+    @respx.mock
+    async def test_send_text_message(self, client):
+        """Successfully send text message."""
+        route = respx.post(
+            "https://graph.facebook.com/v18.0/123456789012345/messages"
+        ).mock(return_value=Response(200, json={
+            "messages": [{"id": "wamid.sent123"}],
+            "contacts": [{"wa_id": "5216641234567"}],
+        }))
+
+        result = await client.send_text_message("5216641234567", "Hola SKEEN")
+        assert result["messages"][0]["id"] == "wamid.sent123"
+        assert route.called
+
+    @respx.mock
+    async def test_send_text_message_too_long(self, client):
+        """Truncate text over 4096 chars."""
+        respx.post(
+            "https://graph.facebook.com/v18.0/123456789012345/messages"
+        ).mock(return_value=Response(200, json={"messages": [{"id": "x"}]}))
+
+        long_text = "A" * 5000
+        await client.send_text_message("5216641234567", long_text)
+        # Should not raise
+
+    @respx.mock
+    async def test_mark_as_read(self, client):
+        """Mark message as read."""
+        route = respx.post(
+            "https://graph.facebook.com/v18.0/123456789012345/messages"
+        ).mock(return_value=Response(200, json={"success": True}))
+
+        result = await client.mark_as_read("wamid.test123")
+        assert result["success"] is True
+        assert route.called
+
+    async def test_button_limit(self, client):
+        """More than 3 buttons raises ValueError."""
+        with pytest.raises(ValueError, match="Maximum 3 buttons"):
+            await client.send_interactive_buttons(
+                "5216641234567",
+                "Choose:",
+                [{"id": "1", "title": "A"}, {"id": "2", "title": "B"},
+                 {"id": "3", "title": "C"}, {"id": "4", "title": "D"}],
+            )