refactor(services): route logging through IPluginLogProxy

F12.2 step 5b — service cluster (~42 sites in 16 files):
MessageManager, GameFunctions/{Chat, GameFunctions, KeybindManager},
EmoteCache, PayloadHandler, AutoTellTabsService, FontManager, Commands,
Util/{WrapperUtil, AutoTranslate, MemoryUtil}, Message, Themes/ThemeRegistry,
Ipc/ExtraChat, Configuration.

The proxy interface gained Dalamud's params-overload signature
(messageTemplate + params object[]) to cover Configuration.cs:86 which
relies on Serilog-style placeholders.

Verified: zero remaining Plugin.Log.X(...) call-sites in HellionChat/,
build green, build-suite 690/690.

HellionChat/Themes/ThemeRegistry.cs

@@ -118,7 +118,7 @@ public sealed class ThemeRegistry
                 catch (Exception ex) when (IsRecoverableFileLock(ex))
                 {
                     // Editor mid-save: keep last known good, retry on next refresh.
-                    Plugin.Log.Debug(
+                    Plugin.LogProxy.Debug(
                         $"Custom theme {Path.GetFileName(path)} is locked, keeping last known good"
                     );
                     if (cached.Theme is not null)