refactor(db): isolate hydraulic playback data access

app/infra/db/timescaledb/repositories/hydraulic_playback.py

@@ -0,0 +1,29 @@
+"""Stream exact playback samples without materializing full-network JSON results."""
+
+from collections.abc import AsyncIterator
+from datetime import datetime
+from typing import Any
+
+from psycopg import AsyncConnection
+
+
+class HydraulicPlaybackRepository:
+    @staticmethod
+    async def iter_node_pressures(conn: AsyncConnection, times: list[datetime]) -> AsyncIterator[dict[str, Any]]:
+        async with conn.cursor() as cursor:
+            await cursor.execute("""
+                SELECT time, node_id, pressure FROM realtime.node_results
+                WHERE time = ANY(%s) ORDER BY time, node_id
+            """, (times,))
+            async for row in cursor:
+                yield row
+
+    @staticmethod
+    async def iter_pipe_metrics(conn: AsyncConnection, times: list[datetime]) -> AsyncIterator[dict[str, Any]]:
+        async with conn.cursor() as cursor:
+            await cursor.execute("""
+                SELECT time, link_id, flow, velocity FROM realtime.link_results
+                WHERE time = ANY(%s) ORDER BY time, link_id
+            """, (times,))
+            async for row in cursor:
+                yield row