Clean up minimap icons: remove WMO filtering, cache active tracking, namespace Lua API

Remove unused indoor/outdoor WMO filtering and gray blip tinting.
Cache active tracking state in a bool refreshed on config change
instead of scanning all entries per-object per-frame. Move
SetObjectTypeBlip into WeirdUtils table to keep it out of the
global namespace. Add minimap tracking section to DLL_README.

src/main.zig

@@ -94,7 +94,11 @@ fn registerLuaFunctions() void {
         registerFunction("GetCursorScale", @intFromPtr(&bigcursor.luaGetCursorScale));
     }
     if (build_opts.minimapicons and minimapicons.isActive()) {
-        registerFunction("SetObjectTypeBlip", @intFromPtr(&minimapicons.luaSetObjectTypeBlip));
+        const lib = [_]lua.LuaReg{
+            .{ .name = "SetObjectTypeBlip", .func = @intFromPtr(&minimapicons.luaSetObjectTypeBlip) },
+            .{ .name = null, .func = 0 },
+        };
+        lua.openlib(lua.getContext(), "WeirdUtils", &lib, 0);
     }
     if (build_opts.worldmarkers and markers.isActive()) {
         // User-facing functions stay global