Never touch spools of printers this bridge never ran

A fresh instance (empty data volume, no printers configured yet) treated
every spool whose "drucker" field named a printer as stale and moved it to
storage. Now only spools at our slot locations or naming a printer this
bridge runs or has written are corrected; written printer names are kept
in the state (seeded from the applied locations on update).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014GcEk5tkfFSYD6NTF66NkC

app/storage.py

@@ -267,4 +267,6 @@ def migrate_state(data: dict, first_printer: str) -> dict:
         data["version"] = 2
     data.setdefault("applied", {})
     data.setdefault("written_locations", [])
+    if "written_printers" not in data:
+        data["written_printers"] = sorted({a["printer"] for a in data["applied"].values() if a.get("printer")})
     return data