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/util/pool_registry_core.cpp

@@ -30,14 +30,6 @@ const std::vector<KnownPool>& knownPools()
             "https://pool.dragonx.is/api/stats", PoolStatsSchema::DragonXIs,
             /*miningcorePoolId=*/"", /*feePercent=*/0.0, /*official=*/true,
         },
-        KnownPool{
-            // The mining (stratum) host is us.dragonx.cc — pool.dragonx.cc is the
-            // Cloudflare-proxied web/API host and does NOT accept stratum on :3333.
-            // Stats still come from pool.dragonx.cc/api/pools (proxied HTTP is fine).
-            "dragonx-cc-pplns", "pool.dragonx.cc", "us.dragonx.cc:3333", "rx/dragonx",
-            "https://pool.dragonx.cc/api/pools", PoolStatsSchema::Miningcore,
-            /*miningcorePoolId=*/"dragonx-pplns", /*feePercent=*/3.0, /*official=*/true,
-        },
     };
     return pools;
 }