refactor(audit): batch 7 — RPC/settings/lite/effects mechanical dedups

Six behavior-preserving consolidations from the audit:

- RPCClient::call() overloads share a private performCall() (payload dump +
  curl_easy_perform + http code) and a static parseRpcResult() (error->RpcError
  extraction). The timeout overload restores the prior timeout in both the
  success and catch paths, exactly as before.
- The six UnifiedCallback methods delegate to one splitUnified() that builds
  the (Callback, ErrorCallback) pair once (null-check preserved).
- One liteTrimCopy() in lite_connection_service replaces 5 file-local
  trim-copy helpers across the lite slice.
- lite_wallet_controller's inline height JSON parse now routes through the
  tested parseLiteHeightResponse().
- theme_effects.cpp: unpackRGB()/scaledAlpha() replace 14 RGB-unpack + 5
  alpha-scale copy-paste blocks.
- settings.cpp load() uses loadScalar()/loadClamped() helpers for ~44 scalar
  fields. Besides removing boilerplate this HARDENS loading: ~44 fields that
  previously only checked contains() now also verify the JSON type, so a
  malformed value in settings.json falls back to the default instead of
  throwing/misreading. Custom cases (enum parses, legacy migrations, arrays)
  stay inline; save() is unchanged.

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

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

src/wallet/lite_connection_service.cpp

@@ -13,17 +13,6 @@ namespace wallet {
 
 namespace {
 
-std::string trimCopy(const std::string& value)
-{
-    auto begin = value.begin();
-    while (begin != value.end() && std::isspace(static_cast<unsigned char>(*begin))) ++begin;
-
-    auto end = value.end();
-    while (end != begin && std::isspace(static_cast<unsigned char>(*(end - 1)))) --end;
-
-    return std::string(begin, end);
-}
-
 bool startsWith(const std::string& value, const char* prefix)
 {
     const std::string prefixValue(prefix);
@@ -34,7 +23,7 @@ bool startsWith(const std::string& value, const char* prefix)
 LiteServerEndpoint trimmedEndpoint(const LiteServerEndpoint& endpoint)
 {
     LiteServerEndpoint normalized = endpoint;
-    normalized.url = trimCopy(normalized.url);
+    normalized.url = liteTrimCopy(normalized.url);
     return normalized;
 }
 
@@ -52,12 +41,23 @@ std::vector<std::pair<std::size_t, LiteServerEndpoint>> usableConfiguredServers(
 
 std::string normalizedChainName(const std::string& chainName)
 {
-    const std::string normalized = trimCopy(chainName);
+    const std::string normalized = liteTrimCopy(chainName);
     return normalized.empty() ? kDragonXLiteChainName : normalized;
 }
 
 } // namespace
 
+std::string liteTrimCopy(const std::string& value)
+{
+    auto begin = value.begin();
+    while (begin != value.end() && std::isspace(static_cast<unsigned char>(*begin))) ++begin;
+
+    auto end = value.end();
+    while (end != begin && std::isspace(static_cast<unsigned char>(*(end - 1)))) --end;
+
+    return std::string(begin, end);
+}
+
 std::vector<LiteServerEndpoint> defaultDragonXLiteServers()
 {
     return {
@@ -83,13 +83,13 @@ LiteConnectionSettings defaultLiteConnectionSettings()
 
 bool isLiteServerUrlUsable(const std::string& serverUrl)
 {
-    const std::string normalized = trimCopy(serverUrl);
+    const std::string normalized = liteTrimCopy(serverUrl);
     return startsWith(normalized, "https://") || startsWith(normalized, "http://");
 }
 
 bool isOfficialLiteServer(const std::string& serverUrl)
 {
-    const std::string url = trimCopy(serverUrl);
+    const std::string url = liteTrimCopy(serverUrl);
     for (const auto& s : defaultDragonXLiteServers())
         if (s.url == url) return true;
     return false;
@@ -126,7 +126,7 @@ const char* liteConnectionAvailabilityName(LiteConnectionAvailability availabili
 LiteServerSelectionResult selectLiteServer(const LiteConnectionSettings& settings)
 {
     auto usableServers = usableConfiguredServers(settings);
-    const std::string stickyServerUrl = trimCopy(settings.stickyServerUrl);
+    const std::string stickyServerUrl = liteTrimCopy(settings.stickyServerUrl);
 
     if (settings.selectionMode == LiteServerSelectionMode::Sticky &&
         isLiteServerUrlUsable(stickyServerUrl)) {