feat(rust): Backpacks — staff and player views, the Bigger backpack step (PLAN_REDESIGNS §11.3)

The site half of §11.3.2, on protocol 14:

- `rust.backpack.size` ("Bigger backpack"): a kit reward with a different
  permission (D337) — one rust_perm_run_grants row per website user with
  backpacks.size.N, no kit, no credit; the perm mirror pushes it and the run's
  revert deletes it. risk change, reversible ledger, a new `rust.backpacks`
  budget, rust.kit.entitle's recipient modes including `linked`. Refused with
  "Backpacks is not installed on this server" in the dry run too (D199), and a
  size the server does not offer is refused by name. Its message is never
  silent: empty is the take-back warning (D338).
- `rust.options.backpacksizes`: each server's sizes above its smallest, from
  the last hello, grouped by server.
- GET /player/rust/backpacks (own links only, 20 reads a minute) and
  GET /admin/users/:id/rust/backpacks (that user's links only). Live, never
  stored; a stranger's id is a 404 and never reaches the game.
- Client: a shared Backpack panel (pick server and account, open, read once)
  on the account page and the admin user page; the grid draws pages of
  pageSize, each slot named by the game (D340, no icons), blueprints by what
  they make (D341), overflow marked. Backpacks joins the server's mod line.

Server 548/548 (13 new in test/backpacks.test.js), client 79/79 (5 new),
routes.manifest regenerated against the pinned core (89 routes), swagger
fragment regenerated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

README.md

@@ -44,6 +44,7 @@ rows here; the website core never learns there is more than one.
 | Public | `GET /api/v1/public/rust/clans/:externalId` — one clan, and its roster inside the roster audience |
 | Player | `GET /api/v1/player/rust/servers` — the server list, on the authenticated tier |
 | Player | `GET /api/v1/player/rust/economics` — your coin balances on every server, per linked account |
+| Player | `GET /api/v1/player/rust/backpacks?serverId=&steamId=` — your own backpack on one server, read live |
 | Admin | `GET/PUT/DELETE /api/v1/admin/rust/servers` and `POST …/:id/test` — the `PUT` carries the wipe schedule |
 | Admin | `GET/PUT /api/v1/admin/rust/visibility` — who may see who is online, fleet-wide and per server |
 | Admin | `PUT …/servers/:id/titles`, `GET …/servers/:id/integrations`, `GET/PUT /api/v1/admin/rust/voice` — chat titles, the optional mods a server has, and the announcement voice |
@@ -83,7 +84,7 @@ forced wipe (first Thursday, 19:00 UK time) — plus an optional one-off date th
 computed wipe. It is computed on every read and never stored, so it cannot go stale after a wipe.
 The server list, the server page, the Android app and `/wipe` all show it.
 
-**Three uMod plugins are optional, and the module works without any of them** (`docs/modules/rust/PLAN.md`
+**Four uMod plugins are optional, and the module works without any of them** (`docs/modules/rust/PLAN.md`
 §33). The bridge plugin's hard requirements are **Kits** and **ZoneManager**.
 
 - **BetterChat** (LaserHydra, 5.2.15). With it: **chat titles** an operator sets per server — "top 3
@@ -100,6 +101,11 @@ The server list, the server page, the Android app and `/wipe` all show it.
   from a user's admin page, a **Coins** leaderboard column and the **Magnate** title — both ranking
   only balances above the server's starting balance. Without it each of those says "Economics is not
   installed on this server" (`docs/modules/rust/PLAN_REDESIGNS.md` §11.2).
+- **Backpacks** (WhiteThunder, 3.17.8). With it: staff open any player's backpack from their admin
+  page and a player sees their own on the account page and in the app — read live, never stored, and
+  never written — and the **Bigger backpack** event step (`rust.backpack.size`) lends one of the
+  server's `backpacks.size.N` sizes until the run ends, pushed like a kit reward. Without it each of
+  those says "Backpacks is not installed on this server" (`docs/modules/rust/PLAN_REDESIGNS.md` §11.3).
 
 News and event lines said in chat can wear one styled group's title and colours — the
 **announcement voice**, chosen in Admin → Rust servers. The line is said by the bridge plugin with no