Multiple printers, printer/slot in Spoolman, kept in sync

- One worker per printer (name, IP, CC2 Control URL, own pinned host key);
  a spool sits in at most one slot of one printer, moves between printers
- Spoolman: location "<printer> Slot N" plus extra fields "drucker"/"slot"
  (created by the bridge), cleared and "Lager" on removal
- Full comparison every minute: the printer wins over manual edits of loaded
  spools; stale printer locations go to storage; own locations untouched
- Automatic migration of v1 settings, state and host key
- Status hint when a tag is still in a tray but unmapped (e.g. after
  "Take out" in CC2 Control)
- SSH test: connection drops during exec give a clean error, not a 500
- Mock environment with several printers; tests for all of the above

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

tests/test_cc2control.py

@@ -107,7 +107,7 @@ def test_spoolman_requests():
         return httpx.Response(200, json={"id": 5})
     sm = Spoolman("http://10.10.6.10:7912", transport=httpx.MockTransport(handler))
     sm.spool(5)
-    sm.set_location(5, "CC2 Slot 1")
+    sm.update_spool(5, {"location": "CC2 Slot 1"})
     sm.use(5, 12.3456)
     assert [(r.method, r.url.path) for r in seen] == [
         ("GET", "/api/v1/spool/5"), ("PATCH", "/api/v1/spool/5"), ("PUT", "/api/v1/spool/5/use")]