fix(ui): theme-aware modal backdrop + full-window lock overlay

Address two GUI-review points:
1. Light themes no longer get a dark modal backdrop: DrawFullWindowBlurBackdrop
   now tints toward the theme app background (WithAlpha(Background(), ...)) for
   both the opaque base and the frost, so a light theme gets a light frosted
   backdrop and a dark theme a dark one. Fixes all blur overlays, not just the
   lock screen.
2. The lock screen now blurs the WHOLE window (sidebar included), not just the
   content area: renderLockScreen opens a full-viewport borderless overlay window
   (##LockOverlay, same pattern as the modal overlays / portfolio, opened from
   within ##ContentArea) with an input blocker, instead of drawing in the content
   child. Removed the theme-independent dark scrim (contradicted point 1).

Auth logic untouched. Needs GUI re-verify of all auth paths + that the whole
screen (incl. sidebar) obscures on lock and unlock returns cleanly.

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

src/app_security.cpp

@@ -767,9 +767,28 @@ void App::checkIdleMining() {
 void App::renderLockScreen() {
     using namespace ui::material;
 
+    // Full-window lock overlay: cover the ENTIRE viewport (sidebar included) so the whole screen is
+    // obscured while locked, not just the tab-content area. A borderless, transparent, focused window
+    // over the main viewport (same pattern as the modal overlays; opened from within ##ContentArea,
+    // like the portfolio modal). Ended at the bottom of this function.
+    ImGuiViewport* vp = ImGui::GetMainViewport();
+    ImVec2 winPos = vp->Pos, winSize = vp->Size;
+    ImGui::SetNextWindowPos(winPos);
+    ImGui::SetNextWindowSize(winSize);
+    ImGui::SetNextWindowFocus();
+    ImGui::PushStyleColor(ImGuiCol_WindowBg, ImVec4(0, 0, 0, 0));  // transparent — we draw the backdrop
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowBorderSize, 0.0f);
+    ImGui::PushStyleVar(ImGuiStyleVar_WindowPadding, ImVec2(0, 0));
+    ImGui::Begin("##LockOverlay", nullptr,
+        ImGuiWindowFlags_NoTitleBar | ImGuiWindowFlags_NoResize | ImGuiWindowFlags_NoMove |
+        ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse |
+        ImGuiWindowFlags_NoNav | ImGuiWindowFlags_NoSavedSettings);
     ImDrawList* dl = ImGui::GetWindowDrawList();
-    ImVec2 winPos = ImGui::GetWindowPos();
+    // Consume input to everything behind (sidebar included) while locked.
-    ImVec2 winSize = ImGui::GetWindowSize();
+    ImGui::SetCursorScreenPos(winPos);
+    ImGui::InvisibleButton("##LockInputBlocker", winSize,
+        ImGuiButtonFlags_MouseButtonLeft | ImGuiButtonFlags_MouseButtonRight | ImGuiButtonFlags_MouseButtonMiddle);
 
     // Live-blur backdrop over the wallet content while locked — matches the app's modal look AND
     // obscures the wallet for privacy (the old backdrop defaulted to 0 = fully visible). Capture-once
@@ -793,10 +812,6 @@ void App::renderLockScreen() {
             cap.captureFrames--;
         }
         DrawFullWindowBlurBackdrop(dl, winPos, winMax, /*allowBlur=*/!justLocked);
-        // A lock screen should read as a clearly-dimmed "locked" state; the blur alone is light in a
-        // light theme, which washes out the card. Add a theme-independent dark scrim over the blur so
-        // the card pops in both themes (standard lock-screen dimming).
-        dl->AddRectFilled(winPos, winMax, IM_COL32(6, 8, 16, 140));
         MarkBlurOverlayDrawn(nullptr);  // suppress foreground theme-effect bleed + re-capture on unlock
     }
 
@@ -1068,6 +1083,10 @@ void App::renderLockScreen() {
             unlockWallet(std::string(lock_passphrase_buf_), timeout);
         }
     }
+
+    ImGui::End();  // ##LockOverlay
+    ImGui::PopStyleVar(3);   // WindowRounding, WindowBorderSize, WindowPadding
+    ImGui::PopStyleColor();  // WindowBg
 }
 
 // ===========================================================================

src/ui/material/draw_helpers.h

@@ -497,7 +497,9 @@ inline void DrawGlassPanel(ImDrawList* dl, const ImVec2& pMin,
 inline void DrawFullWindowBlurBackdrop(ImDrawList* dl, const ImVec2& pMin, const ImVec2& pMax,
                                        bool allowBlur = true)
 {
-    dl->AddRectFilled(pMin, pMax, IM_COL32(9, 10, 16, 255));  // opaque base (shows through if the blur is faint)
+    // Theme-aware tones: a light theme gets a light frosted backdrop, a dark theme a dark one — the
+    // backdrop tints toward the app background rather than a hardcoded dark.
+    dl->AddRectFilled(pMin, pMax, WithAlpha(Background(), 255));  // opaque base (fallback / faint-blur show-through)
     if (allowBlur && IsBackdropActive() && !dragonx::ui::effects::isLowSpecMode()
         && effects::ImGuiAcrylic::IsEnabled() && effects::ImGuiAcrylic::IsAvailable()) {
         // Safe to use a strong custom radius here: while a full-window overlay is active every glass
@@ -507,7 +509,7 @@ inline void DrawFullWindowBlurBackdrop(ImDrawList* dl, const ImVec2& pMin, const
         params.blurRadius = 64.0f;                            // strong full-window blur
         params.fallbackColor.w = 1.0f;                        // full-strength blur so the live content reads
         effects::ImGuiAcrylic::DrawAcrylicRect(dl, pMin, pMax, params, 0.0f);
-        dl->AddRectFilled(pMin, pMax, IM_COL32(6, 8, 18, 70));  // slight dim so the card reads as foreground
+        dl->AddRectFilled(pMin, pMax, WithAlpha(Background(), 70));  // subtle theme-tinted frost so the card reads as foreground
     }
 }