feat(loading): redesigned loader with progress bar, task labels, configurable assets

Loading screen overhaul:
- LoadingView: Nitro V3 logo flush top-left, loading.gif at viewport
  centre, large progress bar (max 900px / 90vw, h-8, gradient + glow)
  anchored bottom-centre with the percentage rendered inside the bar in
  Poppins, plus a friendly stage label underneath. Logo + background +
  progress bar colour overridable via renderer-config keys
  (loading.logo.url, loading.background, loading.progress.color).
- App.tsx: wired a real loadingProgress (0->100) + loadingTask driven by
  the boot pipeline: config init (10), renderer (20), per-warmup-task
  bumps for AssetManager/Localization/AvatarRender/SoundManager (25->70),
  session managers (78/85/92), Communication (98), ready (100). Each bump
  carries a task label looked up via a new taskLabel(key, fallback)
  helper so the Italian baseline ("Sto caricando il guardaroba",
  "Connessione al server", ...) can be translated by editing
  renderer-config; fallback keeps current strings if the key is missing.
- AvatarEffectsView: replace raw fetch(url).json() with
  loadGamedata(url) so the effectmap root manifest (JSON5 with
  // comments) parses correctly and supports the core/custom/seasonal
  tier merge.
- fallbackToLogin: respect login.screen.enabled=false. When login is
  disabled (SSO-only deployments), init failures now route to
  showSessionExpired() (home + diagnostic) instead of rendering an empty
  LoginView placeholder.
- scripts/write-asset-loader.mjs: the pre-React shell rendered into
  #root before the JS bundle takes over was a light-blue login skeleton
  (linear gradient + two grey rectangles) producing a visible flash
  before the real loader appeared. Replaced with the same
  radial-gradient the LoadingView paints — the handoff is now invisible.
- renderer-config.example: document the 13 loader keys so operators can
  copy & translate.

src/components/avatar-effects/AvatarEffectsView.tsx

@@ -1,4 +1,5 @@
 import { AddLinkEventTracker, AvatarDirectionAngle, AvatarEffectActivatedComposer, GetConfiguration, GetSessionDataManager, ILinkEventTracker, RemoveLinkEventTracker } from '@nitrots/nitro-renderer';
+import { loadGamedata } from '@nitrots/utils';
 import { ChangeEvent, FC, useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import { FaChevronLeft, FaChevronRight, FaSearch } from 'react-icons/fa';
 import { LocalizeText, SendMessageComposer } from '../../api';
@@ -65,9 +66,11 @@ export const AvatarEffectsView: FC<{}> = () =>
         {
             try
             {
-                const response = await fetch(url);
-                if(!response.ok) throw new Error(`HTTP ${ response.status }`);
-                const json = await response.json();
+                // The effectmap is served either as a single JSON file or as a
+                // tiered directory with core/custom/seasonal manifests using
+                // JSON5 syntax (// comments allowed). loadGamedata picks the
+                // right mode for us and merges tiers.
+                const json = await loadGamedata<{ effects?: EffectMapEntry[] }>(url);
                 if(cancelled) return;
 
                 const list: EffectMapEntry[] = Array.isArray(json?.effects)