fix: import OptimizedCandidateSource from shared_types directly

mypy strict mode rejects implicit re-exports through intermediate modules.

Author: KRRT7

codeflash/api/aiservice.py

@@ -22,9 +22,9 @@
     FunctionRepairInfo,
     OptimizationReviewResult,
     OptimizedCandidate,
-    OptimizedCandidateSource,
     TestFileReview,
 )
+from codeflash.models.shared_types import OptimizedCandidateSource
 from codeflash.telemetry.posthog_cf import ph
 from codeflash.version import __version__ as codeflash_version