support for purchasing currency packs (#3629)

## Description:

Adds a currency pack system to the store. Players can purchase packs of
in-game currency (Plutonium and Caps) via Stripe checkout.

What's new:

* Pack schema (PackSchema) — new cosmetic type with currency
(hard/soft), amount, and displayName
* "Packs" tab in the Store — renders purchasable currency packs using
existing CosmeticButton infrastructure
* Stripe checkout flow — new createCurrencyPackCheckout API call and
handlePackPurchase handler
* Currency display in Account modal — shows Plutonium and Caps balances
when logged in
I* con components — <plutonium-icon> (animated green glow + rotate) and
<cap-icon> with new SVG assets
* Currency in UserMeResponse — player.currency.hard /
player.currency.soft added to the API schema

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/core/ApiSchemas.ts

@@ -81,6 +81,12 @@ export const UserMeResponseSchema = z.object({
           .optional(),
       })
       .optional(),
+    currency: z
+      .object({
+        soft: z.coerce.number(),
+        hard: z.coerce.number(),
+      })
+      .optional(),
   }),
 });
 export type UserMeResponse = z.infer<typeof UserMeResponseSchema>;

src/core/CosmeticSchemas.ts

@@ -6,6 +6,7 @@ import { PlayerPattern } from "./Schemas";
 export type Cosmetics = z.infer<typeof CosmeticsSchema>;
 export type Pattern = z.infer<typeof PatternSchema>;
 export type Flag = z.infer<typeof FlagSchema>;
+export type Pack = z.infer<typeof PackSchema>;
 export type PatternName = z.infer<typeof CosmeticNameSchema>;
 export type Product = z.infer<typeof ProductSchema>;
 export type ColorPalette = z.infer<typeof ColorPaletteSchema>;
@@ -76,11 +77,18 @@ export const FlagSchema = CosmeticSchema.extend({
   url: z.string(),
 });
 
+export const PackSchema = CosmeticSchema.extend({
+  displayName: z.string(),
+  currency: z.enum(["hard", "soft"]),
+  amount: z.number().int().positive(),
+});
+
 // Schema for resources/cosmetics/cosmetics.json
 export const CosmeticsSchema = z.object({
   colorPalettes: z.record(z.string(), ColorPaletteSchema).optional(),
   patterns: z.record(z.string(), PatternSchema),
   flags: z.record(z.string(), FlagSchema),
+  currencyPacks: z.record(z.string(), PackSchema).optional(),
 });
 
 export const DefaultPattern = {