refactor(ui): semantic status text uses material tokens instead of hardcoded colors

Finishes the feedback-conventions hygiene thread: ~30 hardcoded ImVec4 green /
red / amber literals used for success / error / warning text now use
material::Success/Error/WarningVec4(), so semantic status colors follow the
active skin and stay legible in every theme (several hardcoded greens/reds read
poorly on the light/pastel skins). Covers validate-address, transaction-details,
key-export, export-all-keys, about, the Settings confirmations/lock state, and
the encryption/decryption dialogs. Brand/logo colors and muted white/grey
(disabled) text are left as-is; dynamic-alpha animated indicators are untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/ui/windows/key_export_dialog.cpp

@@ -123,7 +123,7 @@ void KeyExportDialog::render(App* app)
         if (s_fetching) {
             ImGui::TextColored(material::WarningVec4(), "%s%s", TR("key_export_fetching_base"), material::LoadingDots());
         } else if (!s_error.empty()) {
-            ImGui::TextColored(ImVec4(1.0f, 0.3f, 0.3f, 1.0f), TR("error_format"), s_error.c_str());
+            ImGui::TextColored(material::ErrorVec4(), TR("error_format"), s_error.c_str());
             // Not a dead-end: clearing the error falls back through to the Reveal button next frame.
             ImGui::Spacing();
             if (material::TactileButton(TR("retry"), ImVec2(revealBtn.width, 0), S.resolveFont(revealBtn.font))) {
@@ -132,7 +132,7 @@ void KeyExportDialog::render(App* app)
         } else if (s_key.empty() && s_address.length() < 26) {
             // Guard against an empty/blatantly-malformed address before dispatching a doomed reveal.
             // (Also avoids reading s_address[0] on an empty string in the Reveal branch below.)
-            ImGui::TextColored(ImVec4(1.0f, 0.3f, 0.3f, 1.0f), "%s", TR("invalid_address"));
+            ImGui::TextColored(material::ErrorVec4(), "%s", TR("invalid_address"));
         } else if (s_key.empty() && app->getWalletState().isLocked()) {
             // Reveal would just fail with a locked-wallet RPC error — say so and offer to unlock.
             ImGui::PushStyleColor(ImGuiCol_Text, material::Warning());