refactor: address architect review findings (6 items)

R1: Extend @safe to catch ValueError->400, simplify routes_backtest
    (eliminated 4 copies of duplicated try/except)
R2: Consolidate PROVIDER constant into obb_utils.py (single source)
R3: Add days_ago() helper to obb_utils.py, replace 8+ duplications
R4: Extract Reddit/ApeWisdom into reddit_service.py from finnhub_service
R5: Fix missing top-level import asyncio in finnhub_service
R6: (deferred - sentiment logic extraction is a larger change)

All 561 tests passing.

openbb_service.py

@@ -6,12 +6,10 @@ from typing import Any
 import yfinance as yf
 from openbb import obb
 
-from obb_utils import to_list, first_or_empty
+from obb_utils import to_list, first_or_empty, days_ago, PROVIDER
 
 logger = logging.getLogger(__name__)
 
-PROVIDER = "yfinance"
-
 
 async def get_quote(symbol: str) -> dict[str, Any]:
     result = await asyncio.to_thread(
@@ -21,7 +19,7 @@ async def get_quote(symbol: str) -> dict[str, Any]:
 
 
 async def get_historical(symbol: str, days: int = 365) -> list[dict[str, Any]]:
-    start = (datetime.now(tz=timezone.utc) - timedelta(days=days)).strftime("%Y-%m-%d")
+    start = days_ago(days)
     result = await asyncio.to_thread(
         obb.equity.price.historical,
         symbol,