Move middlewares to dedicated folder with one per file

- Create src/middlewares/ folder with separate files:
  - os.ts: base implementer
  - auth.ts: authentication middleware
  - login-request.ts: login request middleware
  - superuser.ts: chains authMiddleware then checks superuser
- Update base.ts to re-export from middlewares
- Update admin procedures to use merged superuserMiddleware
  (no longer need to chain authMiddleware.use(superuserMiddleware))

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api-server/src/middlewares/os.ts

@@ -0,0 +1,10 @@
+/**
+ * Base implementer with typed APIContext
+ * All procedures and middlewares should derive from this
+ */
+
+import type { APIContext } from "../context.js";
+import { implement } from "@orpc/server";
+import { contract } from "@reviq/api-contract";
+
+export const os = implement(contract).$context<APIContext>();