Fix @pattern regexes with spaces

[soumajitgh]

Summary

• Parse slash-delimited @pattern regex literals as a complete value.
• Preserve literal spaces in property and parameter patterns.
• Add regression coverage for both annotation locations.

Root cause

Pattern parsing split the annotation at its first space, truncating regex character classes containing literal spaces.

Testing

• yarn workspace tsoa-tests exec mocha unit/utilities/validatorUtils.spec.ts
• yarn run lint

Fixes #1857