feat(ui): settings polish — button retune, daemon card, RPC 2-row, chat preview

Settings tabs brought closer to the approved mockup:
- ActionButton/renderCardButton retune (settings-scoped): 7px radius, 9px
  padX, Primary → accent-outline chip, Secondary/card buttons more defined.
- Daemon-binary card: compact status right-aligned on the DAEMON BINARY
  heading (Up to date / Version differs / Not installed), filled/rounded
  status box, neutral danger divider (was alarming red), roomier spacing.
- RPC Connection: two-row column-aligned layout (Host | Port, then
  Username | Password) so the password no longer clips off the card edge.
- Chat settings tab: live conversation preview below the Appearance /
  Messaging cards; "Focus input on open" checkbox reflowed onto the console
  color-toggle row.
- Debug Options: "Current theme only" toggle restricts either screenshot
  sweep to the active theme instead of cycling every skin.
- Tabs fill the full content width (content-max-width cap disabled) and the
  sidebar nav panel centers within the true visible area.
- i18n: new keys for the above (untranslated keys fall back to English).

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

src/ui/sidebar.h

@@ -538,11 +538,6 @@ inline bool RenderSidebar(NavPage& current, float sidebarWidth, float contentHei
     float exitRelY = curY + bottomPadding;
     float panelH   = exitRelY + stripH;
 
-    // Vertical centering — offset so panel is centered in the child window
-    float centerOffset = std::max(glassMarginY, (contentHeight - panelH) * 0.5f);
-    if (centerOffset + panelH > contentHeight)
-        centerOffset = std::max(0.0f, contentHeight - panelH);
-
     // ===================================================================
     // PASS 2: Render using computed positions
     // ===================================================================
@@ -552,6 +547,13 @@ inline bool RenderSidebar(NavPage& current, float sidebarWidth, float contentHei
     ImDrawList* dl = ImGui::GetWindowDrawList();
     ImVec2 wp = ImGui::GetWindowPos();
 
+    // Vertical centering — center the panel within the child. app.cpp sizes the child (contentHeight)
+    // to the visible area (child top -> status-bar top) using window-local geometry, so this yields
+    // equal top/bottom gaps at any height on every platform, no viewport dependency.
+    float centerOffset = std::max(glassMarginY, (contentHeight - panelH) * 0.5f);
+    if (centerOffset + panelH > contentHeight)
+        centerOffset = std::max(0.0f, contentHeight - panelH);
+
     float panelLeft   = wp.x + glassMarginL;
     float panelRight  = wp.x + sidebarWidth - glassMarginR;
     float panelTopY   = wp.y + centerOffset;