feat: add Nailong Fund advisor capabilities

app/core/cursor.py

@@ -0,0 +1,17 @@
+"""Strict parsing for record-ID pagination cursors."""
+
+from app.core.errors import InvalidCursorError
+
+MAX_CURSOR_VALUE = 2**63 - 1
+
+
+def parse_cursor(raw: str | None, *, field: str = "cursor") -> int | None:
+    if raw is None or not raw.strip():
+        return None
+    value = raw.strip()
+    if not value.isascii() or not value.isdigit():
+        raise InvalidCursorError(f"{field} must be an ASCII decimal record ID")
+    parsed = int(value)
+    if parsed < 1 or parsed > MAX_CURSOR_VALUE:
+        raise InvalidCursorError(f"{field} is outside the record ID range")
+    return parsed