ui,game,pipeline: player nameplates always-on, level-up ring effect, vanilla tile fallback, warden null guard

- Nameplates: player names always rendered regardless of V-key toggle;
  separate cull distance 40u (players/target) vs 20u (NPCs); cyan name
  color for other players; fade alpha scales with cull distance
- Level-up: add expanding golden ring burst (3 staggered waves, 420u
  max radius) + full-screen flash to renderDingEffect(); M2 LevelUp.m2
  is still attempted as a bonus on top
- Vanilla tile loading: add AssetManager::setBaseFallbackPath() so that
  when the primary manifest is an expansion-specific DBC-only subset
  (e.g. Data/expansions/vanilla/), world terrain files fall back to
  the base Data/ extraction; wired in Application::initialize()
- Warden: map a null guard page at address 0x0 in the Unicorn emulator
  so NULL-pointer reads in the module don't crash with UC_ERR_MAP;
  execution continues past the NULL read for better diagnostics

src/core/application.cpp

@@ -292,6 +292,11 @@ bool Application::initialize() {
             if (std::filesystem::exists(expansionManifest)) {
                 assetPath = profile->dataPath;
                 LOG_INFO("Using expansion-specific asset path: ", assetPath);
+                // Register base Data/ as fallback so world terrain files are found
+                // even when the expansion path only contains DBC overrides.
+                if (assetPath != dataPath) {
+                    assetManager->setBaseFallbackPath(dataPath);
+                }
             }
         }
     }