[FEATURE] Implement Video Compilation service

[aniebietafia]

Problem

Once a story script is approved, the application must compile it into a video presentation. This requires generating graphic elements, synthesizing audio speech, dubbing/translating tracks, and compiling them into a single video file.

Proposed Solution

Implement VideoCompilationService that:

1. Triggers graphic assets rendering by calling the VideoGenerationService adapter (Issue 67) for each scene.
2. Generates narrator audio tracks using TTS services.
3. Integrates with VideoTranslationService (Issue 72) for translation request parameters.
4. Compiles the video assets into a single downloadable file.

User Stories

• As a creator, I want the system to compile my approved script into a finished video complete with narration.

Acceptance Criteria

• The compiler service generates scene graphics and coordinates audio creation.
• The completed video is compiled and saved to cloud storage.

Tasks

• Create VideoCompilationService class.
• Wire up graphic generation and audio synthesis adapters.
• Test the compilation pipeline.