fix(filesystem): make readdir ordering deterministic across iOS and Android

[antonymarion]

Closes #74

Summary

• make readdir results deterministic on Android by sorting entries by mtime, then ctime, then case-insensitive name
• apply the same ordering strategy on iOS so both platforms return the same chronological ordering semantics
• keep API shape unchanged while eliminating platform-dependent native directory iteration order

Test plan

• create files with distinct modification times in the same folder and call Filesystem.readdir on Android
• run the same scenario on iOS and verify identical ordering
• verify tie-breakers by creating files with same mtime and checking ctime, then name ordering
• ensure returned fields (name, type, size, mtime, ctime, uri) are unchanged

[antonymarion]

Context link with issue #74:

• Product problem: in offline-first mobile apps, Filesystem.readdir() can return different orders between iOS and Android, which can break queue/timeline/sync ordering assumptions.
• Technical fix in this PR: make readdir ordering deterministic on both platforms using the same sort strategy (mtime -> ctime -> case-insensitive name).
• Expected result: same chronological ordering semantics on iOS and Android, reducing cross-platform behavioral drift for file-processing logic.