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/features/profile/tests/profile.test.tsx

@@ -1,7 +1,7 @@
 import { screen } from '@testing-library/react'
 import { expect, test } from 'vitest'
-import { json, mockFetch } from '../../../test/fetch'
-import { renderApp } from '../../../test/render'
+import { json, mockFetch } from '@test/fetch'
+import { renderApp } from '@test/render'
 import { PublicProfileView } from '../components/PublicProfileView'
 
 const profile = { id: 'u1', display_nick: 'loki', avatar_url: null, created_at: '2026-01-05T10:00:00Z', badges: ['early'] }