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/contacts_tab.cpp

@@ -1026,7 +1026,7 @@ void RenderContactsTab(App* app)
         const float  tpW   = ImGui::GetContentRegionAvail().x;
         const float  tIpad = 12.0f * dp, tVpad = 10.0f * dp;
         {
-            material::GlassPanelSpec g; g.rounding = 12.0f * dp; g.fillAlpha = 14; g.borderAlpha = 34;
+            material::GlassPanelSpec g; g.rounding = Layout::glassRounding(); g.fillAlpha = 14; g.borderAlpha = 34;
             material::DrawGlassPanel(tpdl, tpMin, ImVec2(tpMin.x + tpW, tpMin.y + listH), g);
         }
         ImGui::SetCursorScreenPos(ImVec2(tpMin.x + tIpad, tpMin.y + tVpad));
@@ -1129,7 +1129,7 @@ void RenderContactsTab(App* app)
             ImDrawList* pdl = ImGui::GetWindowDrawList();
             const ImVec2 pMin = ImGui::GetCursorScreenPos();
             const float  pW = ImGui::GetContentRegionAvail().x;
-            material::GlassPanelSpec g; g.rounding = 12.0f * dp; g.fillAlpha = 14; g.borderAlpha = 34;
+            material::GlassPanelSpec g; g.rounding = Layout::glassRounding(); g.fillAlpha = 14; g.borderAlpha = 34;
             material::DrawGlassPanel(pdl, pMin, ImVec2(pMin.x + pW, pMin.y + listH), g);
         }
         // AlwaysUseWindowPadding: a borderless child ignores WindowPadding without it, so the rows
@@ -1390,7 +1390,7 @@ void RenderContactsTab(App* app)
                 const float rowH  = avR * 2.0f + 16.0f * dp;
                 const float panelH = 2.0f * rowH + gap + 2.0f * padIn;
                 const ImVec2 pOrigin = ImGui::GetCursorScreenPos();
-                material::GlassPanelSpec g; g.rounding = 12.0f * dp; g.fillAlpha = 14; g.borderAlpha = 34;
+                material::GlassPanelSpec g; g.rounding = Layout::glassRounding(); g.fillAlpha = 14; g.borderAlpha = 34;
                 material::DrawGlassPanel(pdl, pOrigin, ImVec2(pOrigin.x + w, pOrigin.y + panelH), g);
                 const ImVec2 rmn(pOrigin.x + padIn, pOrigin.y + padIn);
                 const float rowW = w - 2.0f * padIn;