Add POST /decode/vin endpoint using Gemini 2.5 Flash for VIN string
decoding. Returns structured vehicle data (year, make, model, trim,
body/drive/fuel type, engine, transmission) with confidence score.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add standalone GeminiEngine class for maintenance schedule extraction
from PDF owners manuals using Vertex AI Gemini 2.5 Flash with structured
JSON output enforcement, 20MB size limit, and lazy initialization.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>