refactor(audit): unify config-dir resolution through Platform::getConfigDir

Settings::getDefaultPath and AddressBook::getDefaultPath each hand-rolled the
same per-platform #ifdef (Win SHGetFolderPath / macOS Application Support /
XDG ~/.config) with the DRAGONX_APP_NAME variant suffix. Route both through
util::Platform::getConfigDir() instead — one place owns the split — and add
the missing __APPLE__ branch to getConfigDir so it too returns the
macOS-native ~/Library/Application Support/<AppName>.

This also fixes a latent macOS inconsistency: transaction_history_cache
already resolves via getConfigDir(), which lacked the __APPLE__ branch, so on
macOS the tx cache landed in ~/.config while settings/addressbook went to
~/Library/Application Support. Now all three agree. No migration needed:
Linux/Windows paths are unchanged, and macOS packaging is not yet shipped.
Removes ~50 lines of duplicated #ifdef.

Full-node + Lite build clean; ctest 1/1; hygiene clean.

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

src/config/settings.cpp

@@ -110,33 +110,11 @@ void loadClamped(const json& j, const char* key, T& field, T lo, T hi)
 
 std::string Settings::getDefaultPath()
 {
-#ifdef _WIN32
-    char path[MAX_PATH];
-    if (SUCCEEDED(SHGetFolderPathA(NULL, CSIDL_APPDATA, NULL, 0, path))) {
-        std::string dir = std::string(path) + "\\" DRAGONX_APP_NAME;
-        fs::create_directories(dir);
-        return dir + "\\settings.json";
-    }
-    return "settings.json";
-#elif defined(__APPLE__)
-    const char* home = getenv("HOME");
-    if (!home) {
-        struct passwd* pw = getpwuid(getuid());
-        home = pw->pw_dir;
-    }
-    std::string dir = std::string(home) + "/Library/Application Support/" DRAGONX_APP_NAME;
+    // Single per-platform, per-variant config dir (util::Platform::getConfigDir handles the
+    // _WIN32 / __APPLE__ / XDG split and the DRAGONX_APP_NAME variant suffix in one place).
+    const std::string dir = util::Platform::getConfigDir();
     fs::create_directories(dir);
-    return dir + "/settings.json";
-#else
-    const char* home = getenv("HOME");
-    if (!home) {
-        struct passwd* pw = getpwuid(getuid());
-        home = pw->pw_dir;
-    }
-    std::string dir = std::string(home) + "/.config/" DRAGONX_APP_NAME;
-    fs::create_directories(dir);
-    return dir + "/settings.json";
-#endif
+    return (fs::path(dir) / "settings.json").string();
 }
 
 bool Settings::load()

src/data/address_book.cpp

@@ -10,14 +10,6 @@
 
 #include "../util/logger.h"
 #include "../util/platform.h"
-#include "../config/version.h"   // DRAGONX_APP_NAME (per-variant: ObsidianDragon / ObsidianDragonLite)
-
-#ifdef _WIN32
-#include <shlobj.h>
-#else
-#include <pwd.h>
-#include <unistd.h>
-#endif
 
 namespace fs = std::filesystem;
 using json = nlohmann::json;
@@ -30,36 +22,11 @@ AddressBook::~AddressBook() = default;
 
 std::string AddressBook::getDefaultPath()
 {
-    // Co-locate with settings.json in the per-variant config dir. Use DRAGONX_APP_NAME
-    // (not a hardcoded "ObsidianDragon") so the Lite build writes to ObsidianDragonLite/
-    // rather than polluting the full-node app's directory — matching Settings::getDefaultPath().
-#ifdef _WIN32
-    char path[MAX_PATH];
-    if (SUCCEEDED(SHGetFolderPathA(NULL, CSIDL_APPDATA, NULL, 0, path))) {
-        std::string dir = std::string(path) + "\\" DRAGONX_APP_NAME;
-        fs::create_directories(dir);
-        return dir + "\\addressbook.json";
-    }
-    return "addressbook.json";
-#elif defined(__APPLE__)
-    const char* home = getenv("HOME");
-    if (!home) {
-        struct passwd* pw = getpwuid(getuid());
-        home = pw->pw_dir;
-    }
-    std::string dir = std::string(home) + "/Library/Application Support/" DRAGONX_APP_NAME;
+    // Co-locate with settings.json in the per-variant config dir (Lite -> ObsidianDragonLite/).
+    // util::Platform::getConfigDir() owns the per-platform + per-variant path in one place.
+    const std::string dir = util::Platform::getConfigDir();
     fs::create_directories(dir);
-    return dir + "/addressbook.json";
-#else
-    const char* home = getenv("HOME");
-    if (!home) {
-        struct passwd* pw = getpwuid(getuid());
-        home = pw->pw_dir;
-    }
-    std::string dir = std::string(home) + "/.config/" DRAGONX_APP_NAME;
-    fs::create_directories(dir);
-    return dir + "/addressbook.json";
-#endif
+    return (fs::path(dir) / "addressbook.json").string();
 }
 
 bool AddressBook::load()

src/util/platform.cpp

@@ -245,6 +245,9 @@ std::string Platform::getConfigDir()
         return std::string(path) + "\\" DRAGONX_APP_NAME "\\";
     }
     return getHomeDir() + "\\AppData\\Roaming\\" DRAGONX_APP_NAME "\\";
+#elif defined(__APPLE__)
+    // macOS-native config location (matches what settings.json / addressbook.json use).
+    return getHomeDir() + "/Library/Application Support/" DRAGONX_APP_NAME "/";
 #else
     return getHomeDir() + "/.config/" DRAGONX_APP_NAME "/";
 #endif