feat(drying): show active-cycle filament + target temperature on the AMS drying badge

Bambu's per-tick AMS push carries only the dry_time countdown — the
  filament name and target temperature the user chose are never echoed on
  the wire. The AMS card had no source of truth for them and rendered the
  bare "Drying · 11h 35m left". The badge now shows
  "Drying · PETG @ 65°C · 11h 35m left", matching the cycle the user
  actually started.

  BambuMQTTClient caches {ams_id: {filament, temp}} on send_drying_command
  (mode=1), clears on mode=0 and on the dry_time falling edge to 0 — the
  same per-AMS edge detector that drives the smart-plug-after-drying
  callback. PrinterManager.get_drying_targets exposes it, the four
  printer_state_to_dict call sites thread it through, AMS schema gains
  dry_target_temp + dry_filament, and routes/printers.py builds the same
  fields into the manually-constructed AMSUnit response.

  When no cached target exists (drying started in a previous backend
  lifetime, or initiated outside Bambuddy), the badge falls back to the
  first loaded tray's tray_type + RFID-recommended drying_temp — the
  heuristic the popover already uses to seed defaults.

  i18n: printers.drying.targetSummary = "{{filament}} @ {{temp}}°C" in
  all 11 locales. Parity check 5356 leaves per locale.

  Note: a user reported the H2D's own physical display still labels the
  cycle by the loaded tray's filament (e.g. "PLA" instead of the
  Bambuddy-requested "PETG"). The wire payload is correct end-to-end —
  journalctl shows filament: "PETG" sent and result: success ACKed — and
  the badge in Bambuddy's own UI now reflects what we actually sent,
  independent of the firmware's display choice.

frontend/src/api/client.ts

@@ -366,6 +366,8 @@ export interface AMSUnit {
   dry_status: number;     // 0=Off, 1=Checking, 2=Drying, 3=Cooling, 4=Stopping, 5=Error
   dry_sub_status: number; // 0=Off, 1=Heating, 2=Dehumidify
   dry_sf_reason: number[]; // Cannot-dry reasons (1=InsufficientPower, 8=NeedPluginPower)
+  dry_target_temp: number | null; // Active-cycle target °C (Bambu does not echo)
+  dry_filament: string | null;    // Active-cycle filament name we sent
   module_type: string;    // "ams", "n3f", "n3s"
 }