feat: add NotebookLM research bridge service (CLI wrapper)

Adds lib/services/research.ts — TypeScript service that wraps the
notebooklm CLI to conduct automated research for video topics.

Pipeline: topic → notebook → deep web research → artifacts → structured
ResearchPayload JSON for Gemini script generation.

Features:
- 8-step research pipeline with resilient error handling
- Parallel artifact generation (mind map, briefing, data table, infographic)
- Targeted Q&A extraction (talking points, code examples, pros/cons)
- Scene hint generation (maps content → Remotion scene types)
- Configurable via env vars (NOTEBOOKLM_CLI_PATH, NOTEBOOKLM_STORAGE_PATH)

Note: CLI wrapper is temporary — will be replaced with direct HTTP calls.

807 lines, zero TypeScript errors.

Co-authored-by: research <research@miriad.systems>

Author: Miriad