tests: check that client and server schemas match

[HirenGajjar]

Description

Adds a test suite that verifies the client (codecarbon/core/schemas.py) and server (carbonserver/carbonserver/api/schemas.py) schemas stay compatible, addressing #1190.

What it checks

For each shared model pair (EmissionBase, RunBase, ExperimentBase, ProjectBase, OrganizationBase) — 15 parametrized tests total:

1. Field presence — every client field exists in the server schema
2. Required fields — every required server field exists in the client schema
3. Type compatibility — shared fields have wire-compatible types

Why ast instead of imports

The client and server live in separate uv environments. Using Python's ast module to parse schema files as source avoids any import or path issues — the test runs in the existing client test environment with zero extra dependencies.

Regression proof

This test catches the exact bug fixed in #1189. Temporarily changing on_cloud: Optional[bool] to Optional[str] on the server produces:

FAILED test_shared_field_types_are_compatible[ExperimentBase-...]
AssertionError: [ExperimentBase] Incompatible types between client and server schemas:
  on_cloud: client='bool'  server='Optional[str]'

Related Issue

Closes #1190

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

AI Usage Disclosure

• 🟥 AI-vibecoded: You cannot explain the logic.
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• ♻️ No AI used.

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the contributing.md document.
• I have added tests to cover my changes.
• All new and existing tests passed.