fix(auth): pin better-auth packages to exact 1.6.22

Dokploy builds with npm install, which resolved the ^1.6.22 range to
better-auth 1.7.0 (unlinkAccount API changed to { accountId }), failing
the production build. Locally bun.lock pinned 1.6.22 while
@better-auth/passkey@1.6.9 and @better-auth/expo@1.6.11 used older
peer deps (better-call 1.3.5), which broke client plugin type inference
(authClient.admin missing).

Pin all better-auth packages to exact 1.6.22 so npm and bun resolve
identically, and align passkey/expo plugins with matching peer deps
(better-call 1.3.7). Verified with a full next build --webpack.

package.json

@@ -26,6 +26,6 @@
     "@types/react-dom": "19.2.3"
   },
   "dependencies": {
-    "better-auth": "^1.6.22"
+    "better-auth": "1.6.22"
   }
 }