Initial commit: Howl M365 email management daemon

Full implementation of the Howl email triage system:
- Microsoft Graph API integration with MSAL auth (client-credentials and delegated modes)
- Claude LLM classification via tool use for structured output
- PostgreSQL database with customers, vendors, whitelist, and email_log tables
- Alembic migration for full schema
- APScheduler daemon with graceful shutdown
- Typer CLI (run, dry-run, status commands)
- Business rule classifier with overrides (whitelist protection, low-confidence fallback)
- Action executor (move to folders, flag, escalate with webhook)
- 35 passing unit tests
- README, SETUP, and NEXT_STEPS documentation

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

tests/conftest.py

@@ -0,0 +1,157 @@
+from __future__ import annotations
+
+import json
+import uuid
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Generator
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from howl.config import Settings
+from howl.db.queries import SenderMatch
+from howl.graph.client import GraphClient, Message
+from howl.llm.schemas import EmailClassification
+
+FIXTURES_DIR = Path(__file__).parent / "fixtures"
+
+
+# ---------------------------------------------------------------------------
+# Settings fixture (no real credentials needed)
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def settings() -> Settings:
+    return Settings(
+        azure_tenant_id="test-tenant",
+        azure_client_id="test-client-id",
+        azure_client_secret="test-secret",
+        graph_auth_mode="client_credentials",
+        graph_mailbox="test@example.com",
+        anthropic_api_key="test-anthropic-key",
+        database_url="postgresql+asyncpg://test:test@localhost:5432/howl_test",
+        dry_run=True,
+        log_level="WARNING",
+        log_format="text",
+    )
+
+
+# ---------------------------------------------------------------------------
+# Sample email messages
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def sample_emails() -> list[dict]:
+    with open(FIXTURES_DIR / "sample_emails.json") as f:
+        return json.load(f)
+
+
+@pytest.fixture
+def llm_responses() -> dict:
+    with open(FIXTURES_DIR / "llm_responses.json") as f:
+        return json.load(f)
+
+
+def make_message(raw: dict) -> Message:
+    sender = raw.get("sender", {}).get("emailAddress", {})
+    received_str = raw.get("receivedDateTime")
+    received_at = datetime.fromisoformat(received_str.replace("Z", "+00:00")) if received_str else None
+    return Message(
+        id=raw["id"],
+        conversation_id=raw.get("conversationId"),
+        subject=raw.get("subject"),
+        sender_address=sender.get("address", ""),
+        sender_name=sender.get("name"),
+        received_at=received_at,
+        has_attachments=raw.get("hasAttachments", False),
+        importance=raw.get("importance", "normal"),
+        body_preview=raw.get("bodyPreview"),
+    )
+
+
+@pytest.fixture
+def customer_message(sample_emails) -> Message:
+    return make_message(next(e for e in sample_emails if e["id"] == "msg-001-customer-inquiry"))
+
+
+@pytest.fixture
+def spam_message(sample_emails) -> Message:
+    return make_message(next(e for e in sample_emails if e["id"] == "msg-004-spam"))
+
+
+@pytest.fixture
+def urgent_message(sample_emails) -> Message:
+    return make_message(next(e for e in sample_emails if e["id"] == "msg-007-urgent"))
+
+
+# ---------------------------------------------------------------------------
+# Mock Graph client
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def mock_graph(sample_emails) -> MagicMock:
+    graph = MagicMock(spec=GraphClient)
+    raw_messages = [make_message(e) for e in sample_emails]
+    graph.list_unread_messages.return_value = (raw_messages[:3], None)
+    graph.get_message_body.return_value = "This is the email body text."
+    graph.get_or_create_folder.return_value = str(uuid.uuid4())
+    graph.move_message.return_value = None
+    graph.flag_message.return_value = None
+    graph.mark_as_read.return_value = None
+    return graph
+
+
+# ---------------------------------------------------------------------------
+# Mock LLM client
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def mock_llm_classification(llm_responses) -> EmailClassification:
+    return EmailClassification.model_validate(llm_responses["customer_inquiry"])
+
+
+@pytest.fixture
+def mock_llm(mock_llm_classification) -> MagicMock:
+    from howl.llm.client import LLMClient
+    llm = MagicMock(spec=LLMClient)
+    llm.classify.return_value = (
+        mock_llm_classification,
+        {
+            "model": "claude-sonnet-4-6",
+            "stop_reason": "tool_use",
+            "usage": {"input_tokens": 350, "output_tokens": 80},
+            "tool_input": mock_llm_classification.model_dump(),
+        },
+    )
+    return llm
+
+
+# ---------------------------------------------------------------------------
+# Sender matches
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def customer_match() -> SenderMatch:
+    return SenderMatch(
+        sender_type="customer",
+        entity_id=uuid.uuid4(),
+        entity_table="customers",
+        entity_name="Acme Corp",
+        notes="Key account - handle with priority",
+    )
+
+
+@pytest.fixture
+def unknown_match() -> SenderMatch:
+    return SenderMatch(sender_type="unknown")
+
+
+@pytest.fixture
+def whitelist_match() -> SenderMatch:
+    return SenderMatch(
+        sender_type="whitelist",
+        entity_id=uuid.uuid4(),
+        entity_table="whitelist",
+        entity_name="Trusted partner domain",
+    )