feat(payments): chip wallet, store-compliance gate and benefit application

Stand up the internal chip/benefit mechanic behind the narrow payments interface:
context-aware balances and benefits, an atomic chip spend, admin grants as
zero-price value sales, the one-directional store-compliance gate (VK/TG same-
origin only, web draws direct→vk→tg, VK-iOS frozen, untrusted fail-closed), and
per-origin hint and no-ads application with term stacking. Reads are served from
an in-process, account-keyed write-through cache (mirroring the suspension gate),
so hot paths issue no query to the payments schema.

Flip the online-game hint wallet and the ad-banner suppression from the deprecated
accounts.hint_balance / paid_account columns to the payments benefit (a hint
balance no longer suppresses the banner — only a no-ads benefit does), and fold
chip segments and benefits by origin on account merge, inside the merge tx. Add
the GET/POST /api/v1/user/wallet edge chain (REST → Connect → FlatBuffers) plus
its codec unit test; no wallet UI yet.

Bring the frozen owner decisions log into the repo at
docs/PAYMENTS_DECISIONS_ru.md (it was untracked under .vscode) and reference it
from PLAN.md; record the read-cache design and the present-sources interface in
PLAN.md and docs/PAYMENTS.md (+ RU mirror).

ui/src/lib/model.ts

@@ -152,6 +152,24 @@ export interface FeedbackState {
   reply: FeedbackReply | null;
 }
 
+/** One chip balance in the wallet: the funding source, the chip count, and whether it is
+ *  spendable in the current execution context (false for a frozen VK-iOS balance or untrusted). */
+export interface WalletSegment {
+  source: string;
+  chips: number;
+  spendable: boolean;
+}
+
+/** The user-facing wallet: the context-visible chip segments and the context-applicable
+ *  benefits (the no-ads term end as unix millis / forever flag, and the available hints). */
+export interface Wallet {
+  segments: WalletSegment[];
+  adsForever: boolean;
+  /** No-ads term end as unix milliseconds; 0 = no active term. */
+  adsPaidUntilMs: number;
+  hints: number;
+}
+
 export interface Profile {
   userId: string;
   displayName: string;