Major Update: Configuration System, Gitignore Support, Auto Language Detection + Code Quality

[pescheck-bram]

What does this PR do?

Introduces major new features for smarter PO file processing, adds comprehensive configuration support, and fixes code quality issues.

Major Features Added

• 🔧 Configuration System - Set defaults in pyproject.toml
• 📁 Gitignore Support - Respects .gitignore when scanning files (⚠️ breaking change)
• 🔍 Auto Language Detection - Detects languages from PO metadata and folder structure
• ⏭️ Skip Translated Files - Saves API calls by skipping completed translations
• 💾 Incremental Save - Saves progress during translation to prevent data loss
• 🌐 Enhanced Django Support - Handles special codes and plural forms
• 🔄 Duplicate Message Handling - Smart processing of repeated msgids
• 🚫 English Fallback Prevention - Prevents using source text as translation

New Components Added

• services/language_detector.py (222 lines)
• utils/config_loader.py (298 lines)
• utils/gitignore.py (233 lines)
• utils/po_entry_helpers.py (48 lines)
• 12+ new comprehensive test files

Code Quality Improvements

• ✅ Fixed critical validate_translation() bug
• ✅ Cleaned up imports and unused variables

⚠️ Breaking Change

Now respects .gitignore by default. Use --no-gitignore to process ignored files.

Type of change

• Bug fix
• Code quality improvement
• New feature
• Breaking change