Implement Local Transliteration Model

[shubhh139]

Currently, transliteration only supports external AI4Bharat APIs. Implement local transliteration model similar to the IndicTrans2 translation service for better performance, privacy, and offline capability.

Acceptance Criteria

• Research and implement local transliteration model (e.g., IndicXlit, Google Transliteration API, or similar)
• Add environment variables for local model configuration
• Implement dual-mode support (local vs external API)
• Add model loading and caching mechanisms
• Support for major Indian language scripts (Devanagari, Bengali, Tamil, Telugu, etc.)
• Update documentation with local model setup instructions
• Add performance benchmarks comparing local vs external

Estimation: 16 hours