feat(bootstrap,api,infra): scaffold app composition, health route, and postgres/minio/qdrant adapters

Why:
- first runnable slice of ADR-0012's resource-lifetime rules and ADR-0015's package layout: app-lifetime clients built once in the lifespan, released via explicit dependencies.

Changes:
- Settings split into per-domain nested settings (postgres/minio/ingestion/qdrant/app/logging); FastAPI app wired with /healthz, /readyz and a /v1 router; Postgres/MinIO/Qdrant adapters and SQLAlchemy models for tenants, API keys, source files, ingestion jobs/events.

src/bootstrap/dependencies.py

@@ -0,0 +1,44 @@
+from collections.abc import AsyncIterator
+from dataclasses import dataclass
+
+from fastapi import Request
+from minio import Minio
+from qdrant_client import AsyncQdrantClient
+from sqlalchemy.ext.asyncio import AsyncEngine, AsyncSession, async_sessionmaker
+
+from src.config import Settings
+
+
+@dataclass
+class AppResources:
+    settings: Settings
+    db_engine: AsyncEngine
+    db_sessionmaker: async_sessionmaker[AsyncSession]
+    minio_client: Minio
+    qdrant_client: AsyncQdrantClient
+
+
+def _resources(request: Request) -> AppResources:
+    return request.app.state.resources
+
+
+def get_settings(request: Request) -> Settings:
+    return _resources(request).settings
+
+
+def get_minio_client(request: Request) -> Minio:
+    return _resources(request).minio_client
+
+
+def get_qdrant_client(request: Request) -> AsyncQdrantClient:
+    return _resources(request).qdrant_client
+
+
+async def get_db_session(request: Request) -> AsyncIterator[AsyncSession]:
+    sessionmaker = _resources(request).db_sessionmaker
+    async with sessionmaker() as session:
+        try:
+            yield session
+        except Exception:
+            await session.rollback()
+            raise