feat: Add NaijaLingo TTS service for Nigerian languages

[Omotade-MY]

Summary

This PR adds support for 9jalingo (NaijaLingo) Text-to-Speech service to manim-voiceover. NaijaLingo provides neural speech synthesis for African languages including Nigerian Pidgin (pcm), Yoruba (yo), Hausa (ha), and Igbo (ig).

Changes

• Core Service: Added NaijaLingoService in src/manim_voiceover/services/naijalingo.py with support for:
  • Language selection (lang) and voice IDs (voice).
  • Speed playback multiplier (speed).
  • Secure API key resolution (NAIJALINGO_API_KEY from environment/.env or explicit api_key param).
  • Server warm-up/connection retry handling.
• Dependencies: Added naijalingo optional dependency in pyproject.toml and updated uv.lock.
• Exports: Added commented import in src/manim_voiceover/services/__init__.py.
• Examples: Added multi-language example suite in examples/naijalingo-example.py featuring:
  • QuadraticSolverPidgin (Nigerian Pidgin)
  • QuadraticSolverYoruba (Yoruba)
  • MovingCircleHausa (Hausa)

How to Test

python -m manim -pql examples/naijalingo-example.py MovingCircleHausa