Fix SpoolBuddy tag_type for linked spools + add inventory weight check column

SpoolBuddy's "Link to Spool" used the generic updateSpool API which only
  set tag_uid, leaving tag_type and data_origin empty. Now uses linkTagToSpool
  with tag_type='generic' and data_origin='nfc_link'.

  Added a "Weight Check" inventory column (hidden by default) that compares
  each spool's last scale measurement against calculated gross weight with
  ±50g tolerance. Shows green check for match, yellow warning + sync button
  for mismatch. Backend stores last_scale_weight and last_weighed_at on each
  spool when weight is synced via SpoolBuddy. Includes edge case handling
  when scale weight < core weight. i18n keys added for all 6 locales.

frontend/src/api/client.ts

@@ -1820,6 +1820,8 @@ export interface InventorySpool {
   created_at: string;
   updated_at: string;
   cost_per_kg: number | null;
+  last_scale_weight: number | null;
+  last_weighed_at: string | null;
   k_profiles?: SpoolKProfile[];
 }