feat(frontend): avatar upload QOL — feedback, re-crop, drop, progress, history

Task 12 batch around the existing crop/preview flow:
- Success Notice (auto-dismiss ~2.5s) after an avatar upload.
- "Reposition" re-crops the current avatar without re-picking a file.
- Drag & drop an image straight onto the profile avatar circle.
- Real upload progress via a new XHR-backed api.upload (fetch has none);
  refreshOnce now also stores the renewed token (reload-restore fix).
- Local avatar history (last 5, IndexedDB, this-device-only) strip that
  re-uploads a stored crop. Stored as ArrayBuffer (Blob is not cloneable
  under structuredClone); label makes the per-device scope explicit.
- Added a "success" tone to Notice.

Infra (same session): registered @shared/@features/@pages/@app/@test path
aliases in vite.config + tsconfigs and rewrote deep ../../../ imports;
moved avatar components into components/avatar/ to keep folders at <=4 files.

Tests: avatarHistory cap/order, recrop visibility, drop-opens-cropper,
client upload/progress/401-retry. bun test 103 pass, lint 0 errors, build ok.

frontend/src/shared/easter/tests/breakable.test.tsx

@@ -2,7 +2,7 @@ import { screen } from '@testing-library/react'
 import userEvent from '@testing-library/user-event'
 import { expect, test, vi } from 'vitest'
 import { BreakableBlock } from '../BreakableBlock'
-import { renderApp } from '../../../test/render'
+import { renderApp } from '@test/render'
 
 // motion's useReducedMotion reads matchMedia, which jsdom lacks.
 vi.stubGlobal('matchMedia', (query: string) => ({