fix(app): stop the seed-backup nudge and chat identity retrying every frame

The one-time "back up your seed phrase" nudge only stopped probing on a
success or the exact "not derived from a mnemonic" error. Any other
answer re-armed it for the next frame, so a daemon without the RPC
("Method not found", e.g. the older bundled binary) was sent
z_exportmnemonic at frame rate: ~2,300 requests/s against a test node.
Chat identity setup re-posted its fetch on the next frame after a
transient failure in the same way.

An inconclusive nudge probe now waits 5 minutes before the next; a
transient identity-fetch failure waits 10 seconds.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app_network.cpp

@@ -3136,6 +3136,9 @@ void App::maybeProvisionChatIdentity()
 
     if (chat_service_.hasIdentity() || chat_identity_provisioned_ ||
         chat_identity_fetch_in_flight_ || chat_identity_unavailable_) return;
+    // After a transient failure (connection blip, a busy node) wait before asking again: retrying on the
+    // next frame re-sent the request continuously.
+    if (std::chrono::steady_clock::now() < chat_identity_retry_at_) return;
 
     if (supportsLiteBackend()) {
         // Lite: the backend's `seed` command returns the 24-word mnemonic synchronously.
@@ -3206,6 +3209,7 @@ void App::maybeProvisionChatIdentity()
                 }
                 chat_identity_fetch_in_flight_ = false;
                 if (unavailable) chat_identity_unavailable_ = true;
+                if (transientFail) chat_identity_retry_at_ = std::chrono::steady_clock::now() + std::chrono::seconds(10);
                 // Provision only on success AND while still unlocked: a lock (e.g. auto-lock) can
                 // land during the blocking fetch, and provisioning then would unlock the chat DB +
                 // load decrypted history while the wallet is locked. Leaving the flag cleared here
@@ -4451,6 +4455,9 @@ void App::maybeRemindSeedBackup()
     if (!state_.connected || !state_.encryption_state_known) return;
     if (state_.isLocked()) return;                            // wait until unlocked to read it
     if (seed_backup_reminder_in_flight_) return;
+    // An inconclusive answer (an error other than "not derived from a mnemonic" — e.g. a daemon without
+    // the RPC, or a busy one) used to re-fire this probe on the very next frame, hammering the daemon.
+    if (std::chrono::steady_clock::now() < seed_backup_reminder_retry_at_) return;
     seed_backup_reminder_in_flight_ = true;
     exportSeedPhrase([this](bool ok, bool noMnemonic, const std::string& /*phrase*/,
                             const std::string& /*error*/) {
@@ -4460,6 +4467,8 @@ void App::maybeRemindSeedBackup()
         if (ok || noMnemonic) {
             settings_->setSeedBackupReminded(true);
             settings_->save();
+        } else {
+            seed_backup_reminder_retry_at_ = std::chrono::steady_clock::now() + std::chrono::minutes(5);
         }
         if (ok)
             ui::Notifications::instance().info(TR("seed_backup_reminder"), 12.0f);