fix: replace (str, Enum) with StrEnum to resolve ruff UP042

StrEnum (Python 3.11+) is the modern replacement for the (str, Enum)
pattern. Updates SyncState and PipelineState enums.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/polymarket_insider_tracker/ingestor/metadata_sync.py

@@ -11,7 +11,7 @@ import logging
 from collections.abc import Callable
 from dataclasses import dataclass
 from datetime import UTC, datetime
-from enum import Enum
+from enum import StrEnum
 
 from redis.asyncio import Redis
 
@@ -27,7 +27,7 @@ DEFAULT_CACHE_TTL_SECONDS = 600  # 10 minutes
 DEFAULT_REDIS_KEY_PREFIX = "polymarket:market:"
 
 
-class SyncState(str, Enum):
+class SyncState(StrEnum):
     """State of the metadata synchronizer."""
 
     STOPPED = "stopped"

src/polymarket_insider_tracker/pipeline.py

@@ -11,7 +11,7 @@ import contextlib
 import logging
 from dataclasses import dataclass
 from datetime import UTC, datetime
-from enum import Enum
+from enum import StrEnum
 from typing import TYPE_CHECKING
 
 from redis.asyncio import Redis
@@ -43,7 +43,7 @@ if TYPE_CHECKING:
 logger = logging.getLogger(__name__)
 
 
-class PipelineState(str, Enum):
+class PipelineState(StrEnum):
     """Pipeline lifecycle states."""
 
     STOPPED = "stopped"