feat(finder): question schema and FinderAnswers types

[GMNAPI]

Define all TypeScript types for the 8-question wizard flow.

Includes:

• FinderAnswers interface + per-question answer union types
• QuestionOption<T>, Question<T>, QUESTION_ORDER
• QUESTIONS map with full Catalan copy
• getRentOptions() — dynamic rent thresholds based on location + contractType

Status: ✅ Implemented in web/src/app/finder/questions.ts

Effort: XS (~2h)
Deps: none