Implement locale-aware quoting for the ls command, allowing filenames
to be quoted using locale-specific quotation marks based on the
current LC_CTYPE setting.

Features:
- Add Quotes::Locale variant for locale-aware quoting
- Create locale_quotes module with comprehensive locale mappings
- Support 20+ languages with appropriate quote characters:
  * Romance languages (French, Spanish, etc.): guillemets
  * Germanic languages (German, Czech, etc.): low-9 and high quotes
  * Japanese: corner brackets
  * Chinese/Korean: CJK curly quotes
  * English/default: ASCII double quotes
- Proper UTF-8 handling for multi-byte quote characters
- Environment variable precedence: LC_ALL > LC_CTYPE > LANG
- Localized help text in English and French

Implementation:
- Enhanced CQuoter to dynamically detect and apply locale quotes
- Added --quoting-style=locale CLI option
- Follows C-style quoting semantics (always-quote behavior)
- Safe fallback to ASCII double quotes for unknown locales
- Added spell-checker:ignore comments for technical terms

Testing:
- Verified with multiple locales (en_US, fr_FR, de_DE, ja_JP, zh_CN)
- All existing tests pass
- Help text properly localized

Add test coverage for locale-aware quoting functionality:
- Tests 10 different locales with appropriate quotation marks
- Verifies English, French, German, Japanese, Chinese, Russian, Spanish, Polish, C, and POSIX locales
- Tests escape sequence handling with locale quoting (newline character)
- Validates UTF-8 encoding of multi-byte quote characters

Fix test failures by limiting locale tests to those available in the CI environment.
CI only generates en_US.UTF-8, fr_FR.UTF-8, es_ES.UTF-8, and sv_SE.UTF-8.

Removed tests for: de_DE, ja_JP, zh_CN, pl_PL, ru_RU.UTF-8
- These locales are not generated in .github/workflows/GnuTests.yml
- The locale_quotes module unit tests still validate these quote types
- This keeps the integration test CI-friendly while maintaining comprehensive coverage

Add missing Quotes::Locale test case in test_quotes_display() to ensure
the Display trait implementation is tested for all quote variants.

Add comprehensive unit tests for locale_quotes module:
- Test locale environment variable precedence (LC_ALL > LC_CTYPE > LANG)
- Validate quote character mappings for all supported locales
- Ensure Romance, Germanic, Slavic, and Asian language quotes work correctly
- Test locale string parsing with encoding and modifiers
- Verify fallback behavior for unknown locales

This adds 17 unit tests covering the locale detection and quote mapping
functionality that was previously untested.

…ariables

Add test_ls_quoting_style_locale_env_vars to verify that --quoting-style=locale
correctly responds to different locale environment variables (LC_ALL).

Tests verify:
- French locale (fr_FR.UTF-8) uses guillemets (« »)
- Spanish locale (es_ES.UTF-8) uses guillemets (« »)
- Swedish locale (sv_SE.UTF-8) uses ASCII quotes
- C locale uses ASCII quotes

Note: Environment variable precedence testing (LC_ALL > LC_CTYPE > LANG) is
already comprehensively covered in unit tests (locale_quotes.rs). These
integration tests focus on end-to-end functionality.

- Add locale/typography terms (CTYPE, Guillemets, guillemets) to spell checker dictionary
- Skip newline filename test on Windows where such filenames are invalid