[TASK] define strict JSON schemas for generation cards

[MikeNovikoff]

Description

Before we integrate gRPC, the LLM needs to know exactly what structure to output. We need single source of truth for the "Card" entity

To do

• Create schemas/cards.py
• Define CardModel(BaseModel) and CardDeckModel(BaseModel) with detailed docstrings
• Add examples using ConfigDict(json_schema_extra=...)

Notes

Acceptance Criteria

• Schemas are fully typed, tested, and ready to be injected into the LLM prompt