refactor: fix code review issues across routes and services

- Extract shared route_utils.py (validate_symbol, safe decorator)
  removing duplication from 6 route files
- Extract shared obb_utils.py (to_list, extract_single, safe_last)
  removing duplication from calendar_service and market_service
- Fix _to_list dict mutation during iteration (use comprehension)
- Fix double vars() call and live __dict__ mutation risk
- Fix route ordering: /etf/search and /crypto/search now registered
  before /{symbol} path params to prevent shadowing
- Add date format validation (YYYY-MM-DD pattern) on calendar routes
- Use timezone-aware datetime.now(tz=timezone.utc) in all services
- Add explicit type annotation for asyncio.gather results

obb_utils.py

@@ -0,0 +1,51 @@
+"""Shared OpenBB result conversion utilities."""
+
+from typing import Any
+
+
+def to_list(result: Any) -> list[dict[str, Any]]:
+    """Convert OBBject result to list of dicts with serialized dates."""
+    if result is None or result.results is None:
+        return []
+    items = result.results
+    if not isinstance(items, list):
+        items = [items]
+    out = []
+    for item in items:
+        if hasattr(item, "model_dump"):
+            d = item.model_dump()
+        else:
+            raw = vars(item)
+            d = dict(raw) if raw else {}
+        d = {
+            k: v.isoformat() if hasattr(v, "isoformat") else v
+            for k, v in d.items()
+        }
+        out.append(d)
+    return out
+
+
+def extract_single(result: Any) -> dict[str, Any]:
+    """Extract data from an OBBject result (single model or list)."""
+    if result is None:
+        return {}
+    items = getattr(result, "results", None)
+    if items is None:
+        return {}
+    if hasattr(items, "model_dump"):
+        return items.model_dump()
+    if isinstance(items, list) and items:
+        last = items[-1]
+        return last.model_dump() if hasattr(last, "model_dump") else {}
+    return {}
+
+
+def safe_last(result: Any) -> dict[str, Any] | None:
+    """Get the last item from a list result, or None."""
+    if result is None:
+        return None
+    items = getattr(result, "results", None)
+    if items is None or not isinstance(items, list) or not items:
+        return None
+    last = items[-1]
+    return last.model_dump() if hasattr(last, "model_dump") else None