Add media (object storage) and the background worker (Phase 1)

Media model + migration; an ObjectStore interface with an S3/MinIO (boto3) implementation behind the service layer. Upload (multipart) stores bytes in object storage + a metadata row (checksum, size, content-type, optional attach to person/event/source); list returns presigned URLs; delete is soft. Editor-gated, privacy-filtered, audited. 24 tests pass (object store faked).

Introduces the worker container (same image, 'python -m app.worker'): its first job is the scheduled 30-day soft-delete purge across tables + media object cleanup. Compose gains worker + S3 env on backend/worker; dev override builds the worker too.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Justin Paul <justin@jpaul.me>

backend/tests/conftest.py

@@ -14,9 +14,10 @@ from httpx import ASGITransport, AsyncClient
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
 
 import app.models  # noqa: F401 — register all models on Base.metadata
-from app.api.deps import get_mailer
+from app.api.deps import get_mailer, get_objectstore
 from app.core.db import get_session
 from app.integrations.mailer.base import Mailer
+from app.integrations.objectstore.base import ObjectStore
 from app.main import app
 from app.models import Base
 
@@ -35,7 +36,25 @@ class CapturingMailer(Mailer):
         self.resets.append((to, link))
 
 
+class FakeObjectStore(ObjectStore):
+    def __init__(self) -> None:
+        self.objects: dict[str, tuple[bytes, str]] = {}
+
+    async def ensure_bucket(self) -> None:
+        pass
+
+    async def put_object(self, *, key: str, data: bytes, content_type: str) -> None:
+        self.objects[key] = (data, content_type)
+
+    async def presigned_get_url(self, *, key: str) -> str:
+        return f"https://objects.test/{key}"
+
+    async def delete_object(self, *, key: str) -> None:
+        self.objects.pop(key, None)
+
+
 _mailer = CapturingMailer()
+_store = FakeObjectStore()
 
 
 @pytest.fixture
@@ -61,8 +80,10 @@ async def client():
 
     _mailer.verifications.clear()
     _mailer.resets.clear()
+    _store.objects.clear()
     app.dependency_overrides[get_session] = _override_session
     app.dependency_overrides[get_mailer] = lambda: _mailer
+    app.dependency_overrides[get_objectstore] = lambda: _store
 
     transport = ASGITransport(app=app)
     async with AsyncClient(transport=transport, base_url="http://test") as http_client: