Add Catalan language support (加泰罗尼亚语)

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This PR adds support for Catalan language (català) to Easydict, addressing the request from users in Barcelona and other Catalan-speaking regions.

Changes Made

Core Language System

• Added EZLanguageCatalan constant with full language model implementation
• Chinese name: "加泰罗尼亚语" (official Chinese translation)
• Native name: "Català" (proper Catalan spelling with Unicode support)
• Language code: "ca" (ISO 639-1/BCP-47 standard)
• Voice locale identifier: "ca_ES" (Catalan in Spain)
• Flag emoji: 🏛️ (diplomatically neutral cultural symbol)

Translation Services

• Google Translate: Added Catalan support with language code "ca"
• Bing/Microsoft Translate: Added Catalan support with language code "ca"
• Other services not modified as they don't support Catalan according to their official documentation

Documentation Updates

• Updated total supported language count from 48/50 to 52 languages
• Added Catalan to language support tables in both Chinese (README.md) and English (README_EN.md) documentation
• Updated all language count references throughout the codebase

Language Support Matrix

Service	Catalan Support
Google Translate	✅
Bing/Microsoft Translate	✅
Youdao	❌
DeepL	❌
Apple Translate	❌
Baidu	❌
Volcano	❌

Implementation Details

The implementation follows the established patterns in the codebase:

• Consistent with existing language model structure
• Proper Objective-C memory management
• Swift compatibility maintained through existing bridging
• No breaking changes to existing APIs

Testing

• Created comprehensive test script to verify all changes
• All language references properly added to core language system
• Translation services correctly include Catalan mappings
• Documentation consistently updated across all files

Users can now select Catalan as a source or target language in the language picker and use it with Google Translate and Bing translation services.

Fixes #987.

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