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/lifespan.py

@@ -0,0 +1,56 @@
+from collections.abc import AsyncIterator, Callable
+from contextlib import AbstractAsyncContextManager, asynccontextmanager
+
+import structlog
+from fastapi import FastAPI
+
+from src.bootstrap.dependencies import AppResources
+from src.config import Settings
+from src.infrastructure.minio.client import create_client as create_minio_client
+from src.infrastructure.observability.logging import configure_logging
+from src.infrastructure.postgres.database import create_engine, create_sessionmaker
+from src.infrastructure.qdrant.client import create_client as create_qdrant_client
+
+logger = structlog.get_logger(__name__)
+
+
+def create_lifespan(
+    settings: Settings | None = None,
+) -> Callable[[FastAPI], AbstractAsyncContextManager[None, bool | None]]:
+    @asynccontextmanager
+    async def lifespan(app: FastAPI) -> AsyncIterator[None]:
+        resolved_settings = settings or Settings()
+        configure_logging(resolved_settings.logging)
+
+        db_engine = create_engine(resolved_settings.postgres)
+        db_sessionmaker = create_sessionmaker(db_engine)
+        logger.info("lifespan.postgres.engine.created")
+
+        minio_client = create_minio_client(resolved_settings.minio)
+        logger.info("lifespan.minio.client.created")
+
+        qdrant_client = create_qdrant_client(resolved_settings.qdrant)
+        logger.info("lifespan.qdrant.client.created")
+
+        app.state.resources = AppResources(
+            settings=resolved_settings,
+            db_engine=db_engine,
+            db_sessionmaker=db_sessionmaker,
+            minio_client=minio_client,
+            qdrant_client=qdrant_client,
+        )
+
+        try:
+            yield
+        finally:
+            try:
+                await db_engine.dispose()
+            except Exception:
+                logger.exception("lifespan.postgres.dispose.failed")
+
+            try:
+                await qdrant_client.close()
+            except Exception:
+                logger.exception("lifespan.qdrant.close.failed")
+
+    return lifespan