feat: write Sealed Deck selection to playerProfiles Firestore doc

[ibloud]

Summary

Persist deck selection to playerProfiles/{playerToken}.deck on deck confirmation.

Implementation

• On deck confirm:
  • write deck.primarySuit
  • write deck.cards
  • write deck.savedAt
• Preserve existing stats fields.

Acceptance Criteria

• Deck selection survives session restart.
• Stored deck is readable by matchmaking logic.
• Writes do not overwrite unrelated profile fields.