fix: Skip symbolic links in file discovery and upload

[danskmt]

Description

Prevents scanners from following symbolic links during file discovery and upload, closing a path where files outside the scan root could be read and uploaded.

• GetAllFiles (file_filter.go) now skips symlink entries when FF_FILE_FILTER_SKIP_SYMLINKS is enabled, gated behind a new feature flag internal_snyk_file_filter_skip_symlinks_enabled.
• createUploadFile (batch.go) switches from os.Stat to os.Lstat and rejects symlinks as SpecialFileError (defence in depth, unconditional).
• The test "uploads a symlink to a regular file" is inverted to assert symlinks are skipped.

Checklist

• Tests added and all succeed (make test)
• Regenerated mocks, etc. (make generate)
• Linted (make lint)
• Test your changes work for the CLI
  1. Clone / pull the latest CLI main.
  2. Run go get github.com/snyk/go-application-framework@YOUR_LATEST_GAF_COMMIT in the cliv2 directory.
     • Tip: for local testing, you can uncomment the line near the bottom of the CLI's go.mod to point to your local GAF code.
  3. Run go mod tidy in the cliv2 directory.
  4. Run the CLI tests and do any required manual testing.
  5. Open a PR in the CLI repo now with the go.mod and go.sum changes.
  • Once this PR is merged, repeat these steps, but pointing to the latest GAF commit on main and update your CLI PR.

[snyk-io]

✅ Snyk checks have passed. No issues have been found so far.

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✅	Open Source Security	0	0	0	0	0 issues
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✅	Code Security	0	0	0	0	0 issues

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[snyk-io]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues
✅	Secrets	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.