FastAPI & Pydantic v2 Production Context: Eliminating Deprecated v1 Slop

The Pydantic v1 vs v2 Regression Trap

Because LLM training corpora span years of legacy code, AI models frequently mix Pydantic v1 (`@root_validator`, `.dict()`, `class Config`) with Pydantic v2 (`@model_validator`, `.model_dump()`, `ConfigDict`).

This creates runtime warnings, silent schema coercion bugs, and broken OpenAPI generation.

Enforcing Pydantic v2 Standards: - FORBIDDEN: `@root_validator`, `@validator`, `.dict()`. - MANDATORY: `@model_validator(mode='after')`, `ConfigDict(extra='forbid', frozen=True)`, `.model_dump(mode='json')`. - FORBIDDEN: Naked `except:` blocks that swallow system exceptions.