refactor(ui): consolidate dialog footers + shared empty-state, unify buttons/rounding

Addresses the cross-screen inconsistencies from the layout audit by routing screens onto
the design system's own (previously under-used) shared helpers:

- Dialog footers: migrate ~9 overlay dialogs off hand-rolled placement onto the shared
  helpers — DialogActionFooter (primary+Close), DialogConfirmFooter, or
  BeginOverlayDialogFooter for custom/multi-button rows — so footers share one centered
  treatment. All footer/action buttons now use TactileButton (glass press) instead of the
  bare StyledButton some dialogs used.
- Empty states: add a shared material::DrawEmptyState(icon, title, hint) (centered icon +
  title + wrapped hint) and adopt it in Peers, Transactions, and Market-portfolio, which
  previously showed a bare left-aligned caption.
- Security dialogs: add the missing Cancel to Change Passphrase and Set PIN so the whole
  security family shares a two-button footer (Cancel dismisses without applying).
- Transactions pager: shared TactileButton helpers (matching Explorer).
- Frosted-pane rounding: Contacts/Chat use Layout::glassRounding() instead of hardcoded
  12/10/8px literals, matching Peers.
- "Set Label..." title loses its stray trailing ellipsis.

Preserves every button's label and action; the transfer footer's order becomes
[Confirm][Cancel] to match the shared helper's primary-first convention. Verified at 1280
across full-node + Lite + Windows (ctest green) and an adversarial diff review (clean).

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

src/ui/windows/chat_tab.cpp

@@ -451,7 +451,7 @@ void RenderChatSettingsPreview(App* app, float width) {
     totalH += padIn;
 
     const ImVec2 origin = ImGui::GetCursorScreenPos();
-    material::GlassPanelSpec g; g.rounding = 10.0f * dp; g.fillAlpha = 16; g.borderAlpha = 36;
+    material::GlassPanelSpec g; g.rounding = Layout::glassRounding(); g.fillAlpha = 16; g.borderAlpha = 36;
     material::DrawGlassPanel(dl, origin, ImVec2(origin.x + width, origin.y + totalH), g);
 
     const float leftX = origin.x + padIn;
@@ -795,7 +795,7 @@ void RenderChatTab(App* app)
     {
         ImDrawList* paneDL = ImGui::GetWindowDrawList();
         const ImVec2 pMin = ImGui::GetCursorScreenPos();
-        material::GlassPanelSpec g; g.rounding = 12.0f * Layout::dpiScale(); g.fillAlpha = 20; g.borderAlpha = 34;
+        material::GlassPanelSpec g; g.rounding = Layout::glassRounding(); g.fillAlpha = 20; g.borderAlpha = 34;
         material::DrawGlassPanel(paneDL, pMin, ImVec2(pMin.x + listW, pMin.y + avail.y), g);
     }
     // Inner padding so the list content (buttons, search, conversation cards) doesn't hug the glass
@@ -973,7 +973,7 @@ void RenderChatTab(App* app)
         ImDrawList* paneDL = ImGui::GetWindowDrawList();
         const ImVec2 pMin = ImGui::GetCursorScreenPos();
         const float  pW = ImGui::GetContentRegionAvail().x;
-        material::GlassPanelSpec g; g.rounding = 12.0f * tdp; g.fillAlpha = 12; g.borderAlpha = 34;
+        material::GlassPanelSpec g; g.rounding = Layout::glassRounding(); g.fillAlpha = 12; g.borderAlpha = 34;
         material::DrawGlassPanel(paneDL, pMin, ImVec2(pMin.x + pW, pMin.y + (avail.y - composerAreaH)), g);
     }
     // Inner padding so the header + messages don't hug the glass card's edges (the message child
@@ -1622,7 +1622,7 @@ void RenderChatTab(App* app)
             // FrameBg); a flat FrameBg showed the sharp texture.
             {
                 ImDrawList* cdl = ImGui::GetWindowDrawList();
-                material::GlassPanelSpec g; g.rounding = 8.0f * tdp; g.fillAlpha = 16; g.borderAlpha = 34;
+                material::GlassPanelSpec g; g.rounding = Layout::glassRounding(); g.fillAlpha = 16; g.borderAlpha = 34;
                 material::DrawGlassPanel(cdl, ImVec2(inputX, rowY),
                                          ImVec2(inputX + inputW, rowY + composerBoxH), g);
             }