feat(lifespan): wire data pipeline as optional background task

Step 8 in startup — controlled by DATA_PIPELINE=true env var.
Runs RPC health checks + 6 block/event indexers.

app/lifespan.py

@@ -95,6 +95,17 @@ async def lifespan(_app: FastAPI) -> AsyncIterator[None]:
     except Exception as exc:
         log.info("certstream_start_failed err=%s", exc)
 
+    # 8. Data Pipeline — RPC health + blockchain indexers (optional, env-controlled)
+    try:
+        if os.getenv("DATA_PIPELINE", "false").lower() == "true":
+            from app.data.pipeline import DataPipeline
+            import asyncio
+            pipe = DataPipeline()
+            asyncio.create_task(pipe.start())
+            log.info("data_pipeline_started")
+    except Exception as exc:
+        log.info("data_pipeline_skipped err=%s", exc)
+
     yield
 
     # Shutdown