feat(lite): real backend integration — controller, M0-M2a wiring, smoke tool, tests

- LiteWalletController (src/wallet/lite_wallet_controller.*): App-owned; runs real
  create/open/restore via the linked SDXL bridge with allowBridgeCalls=true; wipes
  seed/passphrase with sodium_memzero; persists on a ready wallet. M2a:
  applyLiteRefreshModelToWalletState maps a parsed refresh bundle into WalletState
  (zatoshi->DRGX, z/t split, tx typing + confirmations, sync progress).
- App wiring: liteWallet() accessor + init() construction when supportsLiteBackend();
  persist -> settings save.
- settings_page: "Validate" reroutes to the controller for real execution (validation-
  only fallback otherwise); wipes UI secret buffers after submit.
- chain name default -> "main" with load-time migration of legacy "DRAGONX"
  (settings.cpp), preventing the backend "Unknown chain" panic.
- M0: build.sh --lite-backend flag; lite_smoke real-backend tool + CMake targets;
  tests/fake_lite_backend.h deterministic harness.
- Tests (test_phase4): injectable-fake bridge, controller lifecycle, chain-name
  migration, refresh->WalletState mapping; plus the lite test-suite churn-cleanup rewrite.

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

src/config/settings.h

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <algorithm>
+#include <cstddef>
 #include <map>
 #include <string>
 #include <set>
@@ -54,6 +55,17 @@ public:
      */
     static std::string getDefaultPath();
 
+    enum class LiteServerSelectionPreferenceMode {
+        Sticky,
+        Random
+    };
+
+    struct LiteServerPreference {
+        std::string url;
+        std::string label;
+        bool enabled = true;
+    };
+
     // Theme
     std::string getTheme() const { return theme_; }
     void setTheme(const std::string& theme) { theme_ = theme; }
@@ -218,6 +230,20 @@ public:
     int getMaxConnections() const { return max_connections_; }
     void setMaxConnections(int v) { max_connections_ = std::max(0, v); }
 
+    // Lite wallet server selection
+    LiteServerSelectionPreferenceMode getLiteServerSelectionMode() const { return lite_server_selection_mode_; }
+    void setLiteServerSelectionMode(LiteServerSelectionPreferenceMode mode) { lite_server_selection_mode_ = mode; }
+    std::string getLiteStickyServerUrl() const { return lite_sticky_server_url_; }
+    void setLiteStickyServerUrl(const std::string& url) { lite_sticky_server_url_ = url; }
+    std::string getLiteChainName() const { return lite_chain_name_; }
+    void setLiteChainName(const std::string& chainName) { lite_chain_name_ = chainName; }
+    std::size_t getLiteRandomSelectionSeed() const { return lite_random_selection_seed_; }
+    void setLiteRandomSelectionSeed(std::size_t seed) { lite_random_selection_seed_ = seed; }
+    bool getLitePersistSelectedServer() const { return lite_persist_selected_server_; }
+    void setLitePersistSelectedServer(bool persist) { lite_persist_selected_server_ = persist; }
+    const std::vector<LiteServerPreference>& getLiteServers() const { return lite_servers_; }
+    void setLiteServers(const std::vector<LiteServerPreference>& servers) { lite_servers_ = servers; }
+
     // Verbose diagnostic logging (connection attempts, daemon state, port owner, etc.)
     bool getVerboseLogging() const { return verbose_logging_; }
     void setVerboseLogging(bool v) { verbose_logging_ = v; }
@@ -358,6 +384,23 @@ private:
     bool keep_daemon_running_ = false;
     bool stop_external_daemon_ = false;
     int  max_connections_ = 0;  // 0 = daemon default
+
+    // Lite wallet server preferences. These are user/server settings only;
+    // wallet secrets, wallet files, and lifecycle state are never stored here.
+    LiteServerSelectionPreferenceMode lite_server_selection_mode_ = LiteServerSelectionPreferenceMode::Sticky;
+    std::string lite_sticky_server_url_ = "https://lite.dragonx.is";
+    std::string lite_chain_name_ = "main";  // SDXL backend chain id; must be main/test/regtest
+    std::size_t lite_random_selection_seed_ = 0;
+    bool lite_persist_selected_server_ = true;
+    std::vector<LiteServerPreference> lite_servers_ = {
+        {"https://lite.dragonx.is", "DragonX Lite", true},
+        {"https://lite1.dragonx.is", "DragonX Lite 1", true},
+        {"https://lite2.dragonx.is", "DragonX Lite 2", true},
+        {"https://lite3.dragonx.is", "DragonX Lite 3", true},
+        {"https://lite4.dragonx.is", "DragonX Lite 4", true},
+        {"https://lite5.dragonx.is", "DragonX Lite 5", true}
+    };
+
     bool verbose_logging_ = false;
     std::set<std::string> debug_categories_;
     bool theme_effects_enabled_ = true;