fix(overview): mining addresses visible at 0 balance; drag-reorder always applies

- Address list: a mining-flagged address stays visible even at 0 balance when
  "hide zero balances" is on (payout addresses shouldn't vanish).
- Drag-reorder: persist dense sort orders (0..N-1) for the whole visible list on
  drop via App::reorderAddresses, instead of a pairwise swap that no-ops when both
  rows are still at the default un-ordered state. First drag now always takes
  effect, and explicit order keeps overriding the starred/type/balance sort.
- Tests: 0-balance mining row survives hide-zero; ordered non-favorite outranks a
  favorite.

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

src/app_network.cpp

@@ -2094,6 +2094,14 @@ void App::swapAddressOrder(const std::string& a, const std::string& b)
     }
 }
 
+void App::reorderAddresses(const std::vector<std::string>& orderedAddrs)
+{
+    if (!settings_) return;
+    for (size_t i = 0; i < orderedAddrs.size(); ++i)
+        settings_->setAddressSortOrder(orderedAddrs[i], static_cast<int>(i));
+    settings_->save();
+}
+
 bool App::isMiningAddress(const std::string& addr) const
 {
     return settings_ && settings_->isMiningAddress(addr);