Initial commit: webmail client (M0/M1)

Three-pane webmail client.
- Backend: FastAPI + async SQLAlchemy + arq worker (Postgres/Redis), IMAP/SMTP
  sync, threading, search, drafts/outbox with undo, attachments, 2FA.
- Frontend: React 18 + Vite + TypeScript + TanStack Query + Tailwind; three-pane
  UI with rich-text composer, light/dark themes, resizable panels.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/tests/conftest.py

@@ -0,0 +1,65 @@
+"""Shared test fixtures and environment defaults.
+
+Ensures the SPEC §14 env vars exist even when tests run outside the conda
+activate hook (e.g. CI), so ``app.config`` imports cleanly.
+"""
+
+from __future__ import annotations
+
+import base64
+import os
+
+os.environ.setdefault("APP_DOMAIN", "test.webmail.local")
+os.environ.setdefault(
+    "DATABASE_URL", "postgresql+asyncpg://webmail:webmail_dev@127.0.0.1:5433/webmail_dev"
+)
+# Force a dedicated Redis DB for tests (index 15) so the suite is isolated from the
+# dev app's Redis (DB 0) and can be flushed between tests without touching real data.
+os.environ["REDIS_URL"] = "redis://127.0.0.1:6380/15"
+os.environ.setdefault("MASTER_KEY", base64.b64encode(b"\x00" * 32).decode())
+os.environ.setdefault("BLOB_ROOT", "./var/blobs-test")
+
+from collections.abc import AsyncIterator  # noqa: E402
+
+import pytest_asyncio  # noqa: E402
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine  # noqa: E402
+from sqlalchemy.pool import NullPool  # noqa: E402
+
+from app.config import get_settings  # noqa: E402
+
+
+@pytest_asyncio.fixture(autouse=True)
+async def _reset_global_engine() -> AsyncIterator[None]:
+    """Dispose process-wide async resources after each test.
+
+    Each test runs on its own event loop; disposing here ensures the next test
+    (and any code using the global engine/redis, e.g. the search backend) rebinds
+    to its own loop rather than reusing a closed one.
+    """
+    from app.redis_client import get_redis
+
+    # Flush the dedicated test Redis DB so rate-limit / session / token state does
+    # not leak between tests (each test starts from a clean slate).
+    await get_redis().flushdb()
+    yield
+    from app.db import dispose_engine
+    from app.redis_client import close_redis
+
+    await dispose_engine()
+    await close_redis()
+
+
+@pytest_asyncio.fixture
+async def db_session() -> AsyncIterator[AsyncSession]:
+    """Rollback-per-test session (nothing persists to the dev database)."""
+    engine = create_async_engine(get_settings().database_url, poolclass=NullPool)
+    conn = await engine.connect()
+    trans = await conn.begin()
+    session = AsyncSession(bind=conn, expire_on_commit=False)
+    try:
+        yield session
+    finally:
+        await session.close()
+        await trans.rollback()
+        await conn.close()
+        await engine.dispose()