=== Checking Foreign Key Constraint Issue ===
Card ID 4 exists: YES
  Card number: 4784405092038144

=== Table Structures ===
bank_cards structure:
  id: int(11) NO PRI
  account_id: int(11) YES 
  player_id: char(36) YES 
  last4: varchar(4) NO 
  card_number: varchar(16) YES 
  card_token: varchar(64) YES 
  type: enum('virtual','physical') NO 
  status: enum('active','locked','replaced','cancelled') NO 
  spending_limits: longtext YES 
  created_at: datetime NO 
  updated_at: datetime NO 

bank_transactions structure:
  id: bigint(20) unsigned NO PRI
  type: enum('sale','refund','transfer') NO 
  amount_cents: bigint(20) NO 
  currency: char(3) NO 
  merchant_id: bigint(20) unsigned YES 
  terminal_id: bigint(20) unsigned YES 
  account_id: bigint(20) unsigned YES 
  card_id: bigint(20) unsigned YES 
  status: enum('approved','declined') NO 
  auth_code: varchar(32) YES 
  external_ref: varchar(64) YES 
  reason: varchar(190) YES 
  meta: longtext YES 
  created_at: timestamp NO 

=== Foreign Key Constraints ===

=== Testing Minimal Insert ===
Insert with NULL card_id: SUCCESS (ID: 67)
Insert with card_id = 4: SUCCESS (ID: 68)