Add card USD pricing and a deck maybeboard

Prices come from Scryfall's prices.usd on printings, shown as a hover badge
on card tiles. The price is picked independently of whichever printing
supplies the display image (the cheapest known price across all printings),
since the display printing is often a promo/variant with no listed price.

The maybeboard lets a deck track cards under consideration without counting
them in deck analysis stats or library assignment totals. Cards move between
mainboard and maybeboard via a per-card toggle; maybeboarding the commander
clears commander status.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/api.ts

@@ -14,6 +14,7 @@ export interface CardRef {
   back_image_uri: string; // back face for transform/MDFC/reversible cards, else ""
   produced_mana: number; // WUBRG bitmask of mana this card can tap for
   produces_colorless: boolean; // can produce {C}
+  price_usd: number; // USD market price, or 0 if unknown
 }
 
 export interface LibraryCard extends CardRef {
@@ -26,6 +27,9 @@ export interface LibraryCard extends CardRef {
 export interface DeckEntry extends CardRef {
   quantity: number;
   is_commander: boolean;
+  /** On the maybeboard: tracked against the deck but excluded from deck
+   * analysis stats and library assignment totals. */
+  is_maybeboard: boolean;
   quantity_owned: number;
 }
 
@@ -142,7 +146,8 @@ export const api = {
     oracleId: string,
     quantity: number,
     isCommander = false,
-  ) => invoke<void>("set_deck_card", { deckId, oracleId, quantity, isCommander }),
+    isMaybeboard = false,
+  ) => invoke<void>("set_deck_card", { deckId, oracleId, quantity, isCommander, isMaybeboard }),
   deckContents: (deckId: number) => invoke<DeckEntry[]>("deck_contents", { deckId }),
   cardDecks: (oracleId: string) => invoke<Deck[]>("card_decks", { oracleId }),
 };