tests: make path expectations OS-agnostic (Windows-compatible)

[kjm99d]

Scope: tests only
Files:

• pkg/x/path/filepathx/path_test.go
• services/thumbnails/pkg/thumbnail/storage/filesystem_test.go
• services/web/pkg/apps/apps_test.go
• services/storage-users/pkg/command/trash_bin_test.go

Summary

This PR makes unit tests OS-agnostic by normalizing path expectations and adjusting fstest.MapFS usage so that tests pass consistently on both Windows and Unix.

Rationale

• fstest.MapFS expects keys with forward slashes (/).
• Several tests implicitly assumed Unix separators, leading to false negatives on Windows.
• Applying filepath.FromSlash to expected values and using OS-aware MapFS keys removes these platform-specific failures without altering production behavior.

What changed

• Normalize expected path strings with filepath.FromSlash(...).
• Use forward-slash MapFS keys while keeping comparisons OS-aware.
• No production or vendor code changes.

How to test locally

go test ./pkg/x/path/filepathx -run TestJailJoin -v
go test ./services/web/pkg/apps      -run TestBuild    -v

Notes

• Tests only. Production/vendor updates live on a separate branch and will be proposed later.