fix(ui): validate and clamp dialog input

Tighten input handling across several dialogs so bad/edge input can't
produce a doomed request or a confusing display:

- app_security: passphrase strength meter now factors character-class
  diversity — an all-one-class string downgrades one tier so "aaaaaaaa"
  no longer scores as high as a mixed one.
- block_info: clamp the height field to the chain tip and hide/deny
  "Next" at the tip (was only yielding a raw RPC error).
- address_label: trim surrounding whitespace before saving; a
  whitespace-only label clears it (mirrors clearing the icon).
- send_tab: re-clamp the amount when a Max send has its fee bumped in the
  confirm popup (kept the total within budget) and NUL-terminate the
  strncpy'd address/memo when a payment URI overwrites the form.
- settings_page: reject an empty/whitespace-only lite wallet path before
  dispatching an unusable open/restore request.
- peers_tab: guard ExtractIP against an empty address.
- transaction_details: disable "View in explorer" when the configured
  explorer URL is empty/whitespace so we never open a garbage link.
- app: seed-backup "Skip" now requires a second, deliberate click with a
  fund-loss warning before it dismisses.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ui/pages/settings_page.cpp

@@ -287,6 +287,19 @@ static void evaluateLiteLifecycleRequestFromPageState(App* app) {
         }
     } liteSecretScrubber{input};
 
+    // Open/Restore both target a wallet path; reject an empty/whitespace-only one early so we
+    // never dispatch an unusable request (the scrubber above still wipes secrets on this return).
+    if (input.request.operation == wallet::LiteWalletLifecycleOperation::OpenExisting ||
+        input.request.operation == wallet::LiteWalletLifecycleOperation::RestoreFromSeed) {
+        std::string trimmedPath(s_settingsState.lite_wallet_path);
+        const auto first = trimmedPath.find_first_not_of(" \t\r\n");
+        if (first == std::string::npos) {
+            s_settingsState.lite_lifecycle_status = "Enter a wallet path";
+            s_settingsState.lite_lifecycle_summary.clear();
+            return;
+        }
+    }
+
     // Restore needs a complete 24-word seed; reject early (the scrubber above still wipes the
     // entered secret on this return path).
     if (input.request.operation == wallet::LiteWalletLifecycleOperation::RestoreFromSeed) {