refactor(data): make AddressBook an App-owned shared instance

Phase 0a of the Contacts/Chat plan. The address book was a file-scoped
singleton (`s_address_book` + `getAddressBook()`) trapped inside
address_book_dialog.cpp, reachable only from that TU. Promote it to an
App-owned member so the upcoming Contacts tab, the Send contact picker,
and a future Chat roster all read one source of truth.

- app.h: add `data::AddressBook address_book_;` + `App::addressBook()`
  accessors, next to the other owned data models.
- app.cpp: load it once in App::init() (idempotent; missing file is fine;
  purely local, no daemon dependency).
- address_book_dialog.cpp: delete the singleton + getAddressBook(); read
  through the App* the dialog already carries (dropping the dead
  `(void)app;`). show() is static so it can't reach the App — drop its
  per-open reload (the book is authoritative for the app lifetime and
  self-saves on mutation). Drop the now-unused <memory> include.

No behavior change; groundwork for the Contacts tab.

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

src/app.cpp

@@ -454,6 +454,10 @@ bool App::init()
         tryConnect();
     }
 
+    // Populate the shared contact store from disk (per-variant addressbook.json).
+    // Idempotent; a missing file is fine (returns true). Purely local — no daemon/RPC dependency.
+    address_book_.load();
+
     DEBUG_LOGF("Initialization complete\n");
     return true;
 }

src/app.h

@@ -14,6 +14,7 @@
 #include <unordered_set>
 #include <nlohmann/json_fwd.hpp>
 #include "data/transaction_history_cache.h"
+#include "data/address_book.h"
 #include "data/wallet_state.h"
 #include "rpc/connection.h"
 #include "services/network_refresh_service.h"
@@ -175,6 +176,10 @@ public:
     WalletState& state() { return state_; }
     const WalletState& state() const { return state_; }
     const WalletState& getWalletState() const { return state_; }
+    // Shared contact store (Contacts tab / Send picker / future Chat roster). App-owned so
+    // every surface reads one source of truth instead of a per-dialog singleton.
+    data::AddressBook& addressBook() { return address_book_; }
+    const data::AddressBook& addressBook() const { return address_book_; }
 
     // Connection state (convenience wrappers)
     bool isConnected() const { return state_.connected; }
@@ -814,6 +819,7 @@ private:
     // PIN vault
     std::unique_ptr<util::SecureVault> vault_;
     data::TransactionHistoryCache transaction_history_cache_;
+    data::AddressBook address_book_;   // shared contact store; loaded once in init(), self-saves on mutation
     std::string pending_transaction_history_cache_passphrase_;
     bool transaction_history_cache_loaded_ = false;
 

src/ui/windows/address_book_dialog.cpp

@@ -12,7 +12,6 @@
 #include "../material/draw_helpers.h"
 #include "imgui.h"
 #include <cstring>
-#include <memory>
 
 namespace dragonx {
 namespace ui {
@@ -26,17 +25,6 @@ char AddressBookDialog::s_edit_label[128] = "";
 char AddressBookDialog::s_edit_address[512] = "";
 char AddressBookDialog::s_edit_notes[512] = "";
 
-// Shared address book instance
-static std::unique_ptr<data::AddressBook> s_address_book;
-
-static data::AddressBook& getAddressBook() {
-    if (!s_address_book) {
-        s_address_book = std::make_unique<data::AddressBook>();
-        s_address_book->load();
-    }
-    return *s_address_book;
-}
-
 static void copyEditField(char* dest, size_t destSize, const std::string& source) {
     if (destSize == 0) return;
     std::strncpy(dest, source.c_str(), destSize - 1);
@@ -49,9 +37,9 @@ void AddressBookDialog::show()
     s_selected_index = -1;
     s_show_add_dialog = false;
     s_show_edit_dialog = false;
-    
-    // Reload address book
-    getAddressBook().load();
+    // The address book is App-owned and loaded once at startup (App::init); it stays
+    // authoritative for the app lifetime and self-saves on every mutation, so there is
+    // nothing to reload here. (show() is static and has no App* to reach it anyway.)
 }
 
 bool AddressBookDialog::isOpen()
@@ -61,8 +49,6 @@ bool AddressBookDialog::isOpen()
 
 void AddressBookDialog::render(App* app)
 {
-    (void)app;  // May use for send-to feature later
-    
     if (!s_open) return;
 
     auto& S = schema::UI();
@@ -137,14 +123,14 @@ void AddressBookDialog::render(App* app)
                 };
                 data::AddressBookEntry entry(trimAB(s_edit_label), trimAB(s_edit_address), s_edit_notes);
                 if (isEdit) {
-                    if (getAddressBook().updateEntry(s_selected_index, entry)) {
+                    if (app->addressBook().updateEntry(s_selected_index, entry)) {
                         Notifications::instance().success(TR("address_book_updated"));
                         s_show_edit_dialog = false;
                     } else {
                         Notifications::instance().error(TR("address_book_update_failed"));
                     }
                 } else {
-                    if (getAddressBook().addEntry(entry)) {
+                    if (app->addressBook().addEntry(entry)) {
                         Notifications::instance().success(TR("address_book_added"));
                         s_show_add_dialog = false;
                     } else {
@@ -165,7 +151,7 @@ void AddressBookDialog::render(App* app)
     };
 
     if (material::BeginOverlayDialog(TR("address_book_title"), &s_open, win.width, 0.94f)) {
-        auto& book = getAddressBook();
+        auto& book = app->addressBook();
         
         // Toolbar
         if (material::StyledButton(TR("address_book_add_new"), ImVec2(0,0), S.resolveFont(actionBtn.font))) {