chore: fix nil safety error in nim compilation

Otherwise iOS build fails like this :
```

[2025-12-13T07:28:13.573Z]
/Users/jenkins/workspace/prs_ios_aarch64_package_PR-19505/vendor/nimbus-build-system/vendor/Nim/lib/system.nim(938,
20) Error: cannot prove 'obj' is not nil

[2025-12-13T07:28:13.573Z] make[1]: ***
[/Users/jenkins/workspace/prs_ios_aarch64_package_PR-19505/mobile/lib/ios/qt6/libnim_status_client.a]
Error 1

[2025-12-13T07:28:13.573Z] make: *** [mobile-build] Error 2

script returned exit code 2
```

Author: siddarthkay

src/app_service/service/token/items/token_list.nim

@@ -1,4 +1,4 @@
-import sequtils, sugar
+import sugar
 
 import app_service/common/utils as common_utils
 
@@ -48,5 +48,5 @@ proc createTokenListItem*(tlDto: TokenListDto): TokenListItem =
       patch: tlDto.version.patch
     ),
     logoUri: common_utils.resolveUri(tlDto.logoUri),
-    tokens: tlDto.tokens.map(t => createTokenItem(t))
+    tokens: collect(for t in tlDto.tokens: createTokenItem(t))
   )