feat(ingestion): index embedded chunks into Qdrant on upload

Why:
- POST /v1/files was reporting chunks_indexed=0/points_created=0 unconditionally
  — chunks were parsed and embedded but never written to Qdrant, so nothing
  was actually searchable after upload.

Changes:
- upload_source_file() now calls index_chunks() after embedding, inside the
  same INGESTION_TIMEOUT_SECONDS window, and marks the job failed
  (error_code=index_failed, 502) if it raises.
- Job counters (points_created, points_soft_deleted) and the response's
  chunks_indexed now reflect the real indexing result instead of a hardcoded
  zero.
- Wired PointStorage through AppResources/lifespan/the files router.

Impact:
- A successful upload is now searchable in Qdrant by the time 201 returns.

src/application/ingestion/errors.py

@@ -49,6 +49,15 @@ class EmbedderError(IngestionError):
     """
 
 
+class PointIndexingError(IngestionError):
+    """Upserting or soft-deleting Qdrant points failed.
+
+    Maps to `502` — like `EmbedderError`, this is an upstream dependency
+    failing, not a malformed request. Kept distinct from `EmbedderError` so the
+    job's `error_code` says which dependency broke.
+    """
+
+
 class IngestionAtCapacityError(IngestionError):
     """`INGESTION_MAX_CONCURRENCY` in-process ingestions are already running.