fix: add VOID_STATE to VerificationType enum

Instrumentation writes verification_type="void_state" for void methods,
but the enum lacked this value, causing ValueError on every SQLite row parse.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: HeshamHM28

codeflash/models/models.py

@@ -740,6 +740,7 @@ class VerificationType(str, Enum):
     )
     INIT_STATE_FTO = "init_state_fto"  # Correctness verification for fto class instance attributes after init
     INIT_STATE_HELPER = "init_state_helper"  # Correctness verification for helper class instance attributes after init
+    VOID_STATE = "void_state"  # Correctness verification for void methods (no return value)
 
 
 @dataclass(frozen=True, slots=True)