feat(rewards): claimable subscription rewards UI (#4566)

## Summary

Subscription perks (signup bonus + daily soft/hard currency) now land as
**unclaimed rewards** the player must explicitly claim, instead of
crediting balances directly (API side: openfrontio/infra#409). This PR
adds the client UI:

- **`RewardsPanel`** — shared Lit element listing pending rewards
(currency icon, `+amount`, server `note` with translated fallbacks for
known reasons), with per-reward **Claim** and **Claim All**. Both claim
endpoints return post-claim balances, so the wallet updates without
re-fetching `/users/@me`.
- **Account modal** — renders the panel above the subscription panel
(rewards survive subscription lapse, so it doesn't depend on an active
sub).
- **`RewardsModal`** — popup at login when rewards are pending. Reuses
`RewardsPanel`, auto-closes when the last reward is claimed. Only opens
on a clean homepage load (`pathname === "/"`, empty hash) so it never
pops over join links, `#modal=...` deep links, or the Stripe
`#purchase-completed` return — that flow reloads clean, so the signup
bonus popup appears right after purchase.
- **Schemas/API** — `RewardSchema` + `rewards[]` on `/users/@me`
(optional for older API versions), `claimReward` / `claimAllRewards` in
`Api.ts`. Reward `id`/`amount` stay opaque bigint strings; a 404 on
single claim means "already claimed elsewhere" (double-click / second
device) and re-syncs instead of erroring.

## Screenshots

Login popup (also embedded in the account modal):

- Panel: currency icon + amount + note per row, Claim / Claim All
buttons
- Amounts formatted via `BigInt` (can exceed `Number.MAX_SAFE_INTEGER`)

## Test plan

- [x] `npm test` — 161 tests pass, including new coverage for
`RewardSchema`, `/users/@me` with/without `rewards`, and both claim
response shapes
- [x] `tsc --noEmit`, ESLint, Prettier clean
- [x] Verified in the running app (Playwright): panel renders in the
account-modal style; single claim against a stubbed endpoint credits
balances and removes the row; Claim All empties the list and auto-closes
the popup; body scroll restored

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/core/ApiSchemas.ts

@@ -75,6 +75,39 @@ const SingleplayerMapAchievementSchema = z.object({
   difficulty: z.enum(Difficulty),
 });
 
+// An unclaimed subscription reward from GET /users/@me. `id` and `amount` are
+// stringified bigints — keep them as strings (amount can in principle exceed
+// Number.MAX_SAFE_INTEGER). `reason` is open-ended server-side; fall back to
+// `note` for unknown values rather than exhausting on an enum.
+export const RewardSchema = z.object({
+  id: z.string(),
+  currencyType: z.enum(["soft", "hard"]),
+  amount: z.string(),
+  reason: z.string(),
+  note: z.string().nullable(),
+});
+export type Reward = z.infer<typeof RewardSchema>;
+
+const CurrencyBalancesSchema = z.object({
+  soft: z.coerce.number(),
+  hard: z.coerce.number(),
+});
+
+// POST /rewards/:rewardId/claim and /rewards/claim-all both return the
+// post-claim balances so the UI can update without re-fetching /users/@me.
+export const ClaimRewardResponseSchema = z.object({
+  currency: CurrencyBalancesSchema,
+});
+export type ClaimRewardResponse = z.infer<typeof ClaimRewardResponseSchema>;
+
+export const ClaimAllRewardsResponseSchema = z.object({
+  claimed: z.array(z.object({ id: z.string() })),
+  currency: CurrencyBalancesSchema,
+});
+export type ClaimAllRewardsResponse = z.infer<
+  typeof ClaimAllRewardsResponseSchema
+>;
+
 export const UserMeResponseSchema = z.object({
   user: z.object({
     discord: DiscordUserSchema.optional(),
@@ -97,12 +130,9 @@ export const UserMeResponseSchema = z.object({
           .optional(),
       })
       .optional(),
-    currency: z
-      .object({
-        soft: z.coerce.number(),
-        hard: z.coerce.number(),
-      })
-      .optional(),
+    currency: CurrencyBalancesSchema.optional(),
+    // Unclaimed rewards — NOT included in `currency` balances until claimed.
+    rewards: RewardSchema.array().optional(),
     clans: z
       .array(
         z.object({