feat: v2.8.0 — Artifacts uploads and plugin links, console tab combos, account avatars

- Artifacts hub: upload a file from the computer; make a skill by uploading a
  Markdown file, files, a folder or a .zip/.skill, or by writing it in the
  dialog; add plugins by picking from the list a marketplace link answers
  (POST /api/artifacts/plugin/inspect); Settings → AI tools → Artifacts Hub.
- Console tabs are combos of up to four split panes (ConsoleTabs, PaneGrid).
- Accounts: an own avatar (PUT/DELETE /api/me/avatar, raster only, ≤ 1 MB,
  <data dir>/avatars/), shown with name and role at the sidebar's foot and on
  the workspace owner groups (GET /api/users/:id/avatar, owner_avatar_at).
- Users page: per-user storage (GET /api/users/storage, measured in a worker)
  and account-pool spend/tokens per account (server/lib/pool-usage.js).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/i18n/locales/en/users.json

@@ -7,6 +7,11 @@
   "sessions": "Sessions",
   "last7d": "7 days",
   "last30d": "30 days",
+  "storage": "Storage",
+  "storageHint": "{{files}} files · measured {{at}}",
+  "storagePartial": "at least — part of the folder could not be read in time",
+  "storageNone": "No home folder of their own",
+  "storageMeasuring": "Measuring…",
   "disabled": "disabled",
   "you": "you",
   "tokens": "{{n}} tokens",
@@ -61,6 +66,8 @@
     "deleted": "{{name}} was deleted."
   },
   "errors": {
+    "EBADIMAGE": "Only a PNG, JPEG, GIF or WebP picture",
+    "ETOOBIG": "The picture must be at most 1 MB",
     "EREAUTH": "Your password is wrong.",
     "ETOOMANY": "Too many wrong passwords. Try again in 15 minutes.",
     "ESELF": "You cannot change your own role or disable yourself.",
@@ -128,7 +135,8 @@
     "livePanes": "Live",
     "quota": "Quota",
     "spend": "5 hours",
-    "spend7d": "{{cost}} in 7 days",
+    "spend7d": "{{cost}} · {{tokens}} tokens in 7 days",
+    "tokens": "{{tokens}} tokens",
     "added": "added {{at}}",
     "expired": "expired",
     "full": "full",