Add URI validation for security (Phase 1.3)

Add validate function to uRI.ml that checks for:
- Acceptable schemes: http, https, ftp, sftp, file, ssh, git, darcs, pijul, fossil
- Path traversal attacks (../, ..\ patterns)

Returns Result type with specific error variants for invalid schemes
and path traversal attempts.

All 17 tests pass.

0 files changed, 0 insertions, 0 deletions