fix: Allow hyphen and underscore in filename

[hmacr]

Allows hyphen and underscore as valid characters for filename

Related: appwrite/appwrite#10501

Summary by CodeRabbit

• New Features

  • Expanded filename validation to allow dashes (-) and underscores (_), in addition to letters, numbers, and dots.
  • Validation remains strict: only these characters are accepted; empty or non-text inputs are rejected.

• Tests

  • Updated test cases to cover newly accepted filename patterns (e.g., test-test, test_test, mixed combinations).