fix(ui): overview/mining polish + default-pool cleanup

- balance: inset the address-row favorite (star) button by the card's inner
  padding so it mirrors the left margin instead of hugging the card edge.
- mining: remove pool.dragonx.cc from the built-in default pools (pool.dragonx.is
  is now the sole default); update the pool-registry test accordingly.
- mining: middle-truncate saved pool-URL and payout-address dropdown rows (new
  shared material::TruncateToWidth helper) so a full z-address no longer runs
  under the trailing delete (X) button.
- mining: fix the thread-grid cells overflowing the card at >100% display
  scaling — the reserved Mine-button width used a raw clamp that didn't scale;
  scale it by dp so cols is estimated correctly (no-op at 100%).

Full-node build + test suite green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/ui/windows/balance_address_list.cpp

@@ -70,6 +70,7 @@ AddressRowLayout ComputeAddressRowLayout(float rowX,
                                          float spacingSm,
                                          float spacingXs)
 {
+    (void)spacingXs;  // trailing button now insets by rowPadLeft (mirrors the left margin)
     AddressRowLayout layout;
     layout.contentStartX = rowX + rowPadLeft;
     layout.contentStartY = rowY + spacingMd;
@@ -77,7 +78,9 @@ AddressRowLayout ComputeAddressRowLayout(float rowX,
 
     const float buttonY = rowY + (rowHeight - layout.buttonSize) * 0.5f;
     const float rightEdge = rowX + rowWidth;
-    const float favoriteX = rightEdge - layout.buttonSize - spacingXs;
+    // Inset the trailing (favorite/star) button by the card's inner padding — the same margin the
+    // left content uses (rowPadLeft) — so it mirrors the left edge instead of hugging the card edge.
+    const float favoriteX = rightEdge - layout.buttonSize - rowPadLeft;
     const float visibilityX = favoriteX - spacingSm - layout.buttonSize;
 
     layout.favoriteButton = {favoriteX, buttonY, layout.buttonSize, layout.buttonSize};