feat: tell users a new version exists, and let them rate the wallet from inside it (#17)

Two gaps, both invisible until you look for them.

There was no update mechanism at all. Someone on an old build stayed on it until they
happened to open the Play Store on their own. For a wallet that is worse than an
inconvenience: today's multisig signing fix would have reached nobody who was not
already looking.

InAppUpdates asks Play on every foreground. A user a few days behind gets the flexible
flow — the download runs in the background and the wallet stays usable, because
interrupting someone mid-transfer to force an update is its own kind of harm. Past
fourteen days of staleness, or on a release marked priority 4+ in Play Console, it
switches to immediate. onResume finishes an interrupted immediate update and installs a
flexible one that completed while the app was backgrounded; without that the first
leaves a user stuck and the second never installs.

Ratings had the same shape of gap: people who would happily rate the wallet never do,
because nothing ever asks. Play's in-app card asks without sending them to the store.

Play answers neither "has this user rated" nor "what did they choose" — by design. It
also throttles to a handful of showings a year and silently drops the rest. So the gates
in AppReviewTracker are not there to avoid nagging, which Play already handles; they
exist to spend those few real chances well: three successful operations, three days
since first use, ninety since the last ask, and not within two days of an error.

Recording sits in RealExtrinsicService, the single point every on-chain action passes
through, so transfers and staking are covered without a hook per screen. The tracker
swallows everything it touches — a rating counter must never be able to fail a transfer.

Both features no-op outside a Play install, so neither can be verified from a Firebase
build; that needs an internal testing track.

Version 1.2.0.

distribution/whatsnew/whatsnew-en-US

@@ -1 +1,5 @@
-Pezkuwi Wallet — the official app for the Digital Kurdistan State. Manage your HEZ tokens, stake, and participate in on-chain governance.
+Multisig approvals work again on Pezkuwi chains. Signers could open an operation but not approve it — that is fixed.
+
+The wallet now tells you when a newer version is available and installs it without leaving the app.
+
+You can also rate the wallet from inside the app, after you have actually used it.

distribution/whatsnew/whatsnew-ku

@@ -1 +1,5 @@
-Pezkuwi Wallet — ئەپی فەرمی دەوڵەتی دیجیتاڵی کوردستان. تۆکنەکانی HEZ بەڕێوەببە، ستەیک بکە و بەشداری بەڕێوەبردنی زنجیرە بکە.
+Pesendkirina multisig li ser zincîrên Pezkuwî dîsa dixebite. Îmzeker dikaribûn karê vekin lê pesend nekin; ev hate çareserkirin.
+
+Berîk niha dema guhertoyeke nû derkeve agahdar dike û nûvekirinê bêyî derketina ji sepanê saz dike.
+
+Hûn dikarin berîkê ji hundirê sepanê, piştî ku bi rastî bi kar anî, nirxînin.

distribution/whatsnew/whatsnew-tr-TR

@@ -1 +1,5 @@
-Pezkuwi Wallet — Dijital Kürdistan Devleti'nin resmi uygulaması. HEZ tokenlarınızı yönetin, stake edin ve zincir üstü yönetime katılın.
+Pezkuwi zincirlerinde multisig onayı yeniden çalışıyor. İmzacılar işlemi açabiliyor ama onaylayamıyordu; düzeltildi.
+
+Cüzdan artık yeni sürüm çıktığında haber veriyor ve güncellemeyi uygulamadan çıkmadan kuruyor.
+
+Cüzdanı, gerçekten kullandıktan sonra uygulama içinden puanlayabilirsiniz.