v1.2.0: UX audit — security fixes, accessibility, and polish

Security (P0):
- Fix sidebar remaining interactive behind lock screen
- Extend auto-lock idle detection to include active widget interactions
- Distinguish missing PIN vault from wrong PIN; auto-switch to passphrase

Blocking UX (P1):
- Add 15s timeout for encryption state check to prevent indefinite loading
- Show restart reason in loading overlay after wallet encryption
- Add Force Quit button on shutdown screen after 10s
- Warn user if embedded daemon fails to start during wizard completion

Polish (P2):
- Use configured explorer URL in Receive tab instead of hardcoded URL
- Increase request memo buffer from 256 to 512 bytes to match Send tab
- Extend notification duration to 5s for critical operations (tx sent,
  wallet encrypted, key import, backup, export)
- Add Reduce Motion accessibility setting (disables page fade + balance lerp)
- Show estimated remaining time during mining thread benchmark
- Add staleness indicator to market price data (warning after 5 min)

New i18n keys: incorrect_pin, incorrect_passphrase, pin_not_set,
restarting_after_encryption, force_quit, reduce_motion, tt_reduce_motion,
ago, wizard_daemon_start_failed

src/ui/sidebar.h

@@ -380,7 +380,7 @@ inline void DrawGlassBevelButton(ImDrawList* dl, ImVec2 mn, ImVec2 mx,
 // collapsed: when true, sidebar is in icon-only mode (narrow width).
 // The caller can toggle collapsed via a reference if a toggle button is desired.
 inline bool RenderSidebar(NavPage& current, float sidebarWidth, float contentHeight,
-                          SidebarStatus& status, bool& collapsed)
+                          SidebarStatus& status, bool& collapsed, bool locked = false)
 {
     using namespace material;
     bool changed = false;
@@ -610,8 +610,12 @@ inline bool RenderSidebar(NavPage& current, float sidebarWidth, float contentHei
             ImGui::SetMouseCursor(ImGuiMouseCursor_Hand);
         }
 
-        // Click detection
-        if (hovered && ImGui::IsMouseClicked(ImGuiMouseButton_Left)) {
+        // Click detection — block pages that require unlock when locked
+        bool pageNeedsUnlock = locked &&
+            item.page != NavPage::Console &&
+            item.page != NavPage::Peers &&
+            item.page != NavPage::Settings;
+        if (hovered && ImGui::IsMouseClicked(ImGuiMouseButton_Left) && !pageNeedsUnlock) {
             current = item.page;
             changed = true;
         }
@@ -620,7 +624,7 @@ inline bool RenderSidebar(NavPage& current, float sidebarWidth, float contentHei
         float iconS = iconHalfSize;  // icon half-size in pixels
         float iconCY = cursor.y + btnH * 0.5f;
         float textY = cursor.y + (btnH - ImGui::GetTextLineHeight()) * 0.5f;
-        ImU32 textCol = selected ? Primary() : OnSurfaceMedium();
+        ImU32 textCol = selected ? Primary() : (pageNeedsUnlock ? OnSurfaceDisabled() : OnSurfaceMedium());
 
         if (showLabels) {
             // Measure total width of icon + gap + label, then center.