fix: resolve language_version in testgen_repair endpoint (#2494)

## Summary
- The `/testgen_repair` endpoint was missed when `language_version`
support was added in #2488
- Clients that stopped sending `python_version`
(codeflash-ai/codeflash#1914) hit `400 - Python version is required`
- Adds `language_version` field and `resolve_python_version` validator
to `TestRepairSchema`, matching the pattern in
`OptimizeSchema`/`TestGenSchema`
- Replaces `python_version=data.python_version` with
`language_version=data.language_version` when constructing
`TestGenSchema` in the repair handler

## Test plan
- [ ] Deploy and verify testgen repair calls no longer return 400
- [ ] Verify old clients sending `python_version` still work (backward
compat via validator)

django/aiservice/core/shared/testgen_review/models.py

@@ -1,6 +1,9 @@
 """Request/response schemas for the testgen review and repair endpoints."""
 
+from typing import Self
+
 from ninja import Schema
+from pydantic import model_validator
 
 from aiservice.models.functions_to_optimize import FunctionToOptimize
 
@@ -82,6 +85,7 @@ class TestRepairSchema(Schema):
     test_timeout: int
     trace_id: str
     python_version: str | None = None
+    language_version: str | None = None
     language: str = "python"
     codeflash_version: str | None = None
     call_sequence: int | None = None
@@ -89,6 +93,13 @@ class TestRepairSchema(Schema):
     previous_repair_errors: dict[str, str] = {}
     module_source_code: str = ""
 
+    @model_validator(mode="after")
+    def resolve_python_version(self) -> Self:
+        """Resolve python_version from language_version for backward compatibility."""
+        if self.python_version is None and self.language_version is not None and self.language == "python":
+            self.python_version = self.language_version
+        return self
+
 
 class TestRepairResponseSchema(Schema):
     generated_tests: str

django/aiservice/core/shared/testgen_review/repair.py

@@ -191,7 +191,7 @@ async def testgen_repair(
             test_framework=data.test_framework,
             test_timeout=data.test_timeout,
             trace_id=data.trace_id,
-            python_version=data.python_version,
+            language_version=data.language_version,
             language=data.language,
             codeflash_version=data.codeflash_version,
         )