feat: reorder child entries with a configurable role permission

- Persist sibling order for child entries (archived_entries.position):
  backfilled to the previous archived_at order, new children appended
  (initial playlist order kept; sync appends after user order).
- PUT /api/archives/:id/entries/:uid/children/order takes the full child
  UID list in one IMMEDIATE transaction (401 guest, 403 role not allowed,
  404 unknown or invisible parent, 400 unless exactly the current children).
- Reorder permission is a role mask in the auth instance settings
  (reorder_children_role_bits, default Admin|Owner). Only the Owner can
  change it, built-in or custom roles, never Guest. /api/auth/me and login
  expose can_reorder_children. Settings PATCH is now one IMMEDIATE txn.
- Main page: drag handle for mouse/trackpad on viewports >640px, up/down
  arrows otherwise (pure CSS, arrows are the fallback), Alt+Up/Down
  everywhere; optimistic with revert. Settings > Instance > Permissions
  for the Owner (read-only for admins).
- Fix: renaming a child entry now updates its row immediately.
- Remove Storybook (deps, config, stories, docs).

frontend/package.json

@@ -6,24 +6,14 @@
   "scripts": {
     "dev": "vite",
     "build": "vite build",
-    "preview": "vite preview",
-    "storybook": "storybook dev -p 6006",
-    "storybook:build": "storybook build"
+    "preview": "vite preview"
   },
   "dependencies": {
     "react": "^18.3.1",
     "react-dom": "^18.3.1"
   },
   "devDependencies": {
-    "@storybook/addon-essentials": "^7.6.20",
-    "@storybook/addon-interactions": "^7.6.20",
-    "@storybook/blocks": "^7.6.20",
-    "@storybook/preview-api": "^7.6.20",
-    "@storybook/react": "^7.6.20",
-    "@storybook/react-vite": "^7.6.20",
-    "@storybook/test": "^7.6.20",
     "@vitejs/plugin-react": "^4.3.4",
-    "storybook": "^7.6.20",
     "vite": "^5.4.11"
   }
 }