feat(portfolio): persisted portfolio entries + pure sum helpers

Foundation for the Market tab's configurable portfolio (custom labels tied to
groups of addresses):

- Settings gains a PortfolioEntry {label, addresses[]} list, persisted in
  settings.json as a JSON array-of-objects (same mechanism as lite_servers_),
  with get/setPortfolioEntries().
- data/portfolio.h (header-only, ImGui-free): SumPortfolioBalance() sums a
  group's DRGX balance against the live per-address list (unknown addresses
  contribute 0), plus PortfolioEntryContains/Add/Remove group helpers.
- Unit-tested (testPortfolioHelpers): empty/known/unknown-address sums, and the
  add/remove/contains membership semantics.

UI (editor dialog, Market card rework, Overview right-click) comes next.
Full-node + lite build clean; ctest green.

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

src/data/portfolio.h

@@ -0,0 +1,61 @@
+// DragonX Wallet - ImGui Edition
+// Copyright 2024-2026 The Hush Developers
+// Released under the GPLv3
+//
+// Portfolio helpers — pure balance math for the Market tab's configurable portfolio.
+// A portfolio entry is a user label tied to a group of wallet addresses (persisted in
+// Settings as PortfolioEntry); these helpers sum/query that group against the live
+// per-address balance list. No I/O, no ImGui — unit-testable.
+
+#pragma once
+
+#include "wallet_state.h"   // AddressInfo
+
+#include <string>
+#include <unordered_set>
+#include <vector>
+
+namespace dragonx {
+namespace data {
+
+// Sum the DRGX balance of `entryAddresses` by looking them up in the wallet's per-address
+// list. Addresses not present in the wallet contribute 0 (e.g. removed/rescanned). Pure.
+inline double SumPortfolioBalance(const std::vector<std::string>& entryAddresses,
+                                  const std::vector<AddressInfo>& walletAddresses)
+{
+    if (entryAddresses.empty()) return 0.0;
+    std::unordered_set<std::string> want(entryAddresses.begin(), entryAddresses.end());
+    double sum = 0.0;
+    for (const auto& a : walletAddresses)
+        if (want.count(a.address)) sum += a.balance;
+    return sum;
+}
+
+// Whether `address` is part of the entry's address group.
+inline bool PortfolioEntryContains(const std::vector<std::string>& entryAddresses,
+                                   const std::string& address)
+{
+    for (const auto& a : entryAddresses)
+        if (a == address) return true;
+    return false;
+}
+
+// Add `address` to the group if absent (returns true if it was added).
+inline bool PortfolioEntryAdd(std::vector<std::string>& entryAddresses, const std::string& address)
+{
+    if (address.empty() || PortfolioEntryContains(entryAddresses, address)) return false;
+    entryAddresses.push_back(address);
+    return true;
+}
+
+// Remove `address` from the group if present (returns true if it was removed).
+inline bool PortfolioEntryRemove(std::vector<std::string>& entryAddresses, const std::string& address)
+{
+    for (auto it = entryAddresses.begin(); it != entryAddresses.end(); ++it) {
+        if (*it == address) { entryAddresses.erase(it); return true; }
+    }
+    return false;
+}
+
+} // namespace data
+} // namespace dragonx