soak: pass flow names as SQL parameters so observability cleanup parses

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

backend/scripts/soak.py

@@ -849,13 +849,13 @@ def clear_redis() -> None:
 
 def clear_observability() -> None:
     """The collector wrote rollups, runs and events for the soak flows."""
-    names = ", ".join(repr(flow) for flow in FLOWS)
+    marks = ", ".join("?" for _ in FLOWS)
     script = "\n".join(
         [
             "import sqlite3",
             "db = sqlite3.connect('/data/fluksio.db')",
             *(
-                f"db.execute('DELETE FROM {table} WHERE flow IN ({names})')"
+                f"db.execute('DELETE FROM {table} WHERE flow IN ({marks})', {FLOWS!r})"
                 for table in ("metric_minute", "flow_run", "engine_event")
             ),
             "db.commit()",