Hoist math import to module level in the PEP 249 module

The sync connect() function imported math inside the function body,
while the async module's aio/__init__.py imports it at module top. Move
the sync import to the top so both modules use the same idiom.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitedbapi/__init__.py

@@ -1,5 +1,7 @@
 """PEP 249 compliant interface for dqlite."""
 
+import math
+
 from dqlitedbapi.connection import Connection
 from dqlitedbapi.cursor import Cursor
 from dqlitedbapi.exceptions import (
@@ -118,8 +120,6 @@ def connect(
     Returns:
         A Connection object
     """
-    import math
-
     if not math.isfinite(timeout) or timeout <= 0:
         raise ProgrammingError(f"timeout must be a positive finite number, got {timeout}")
     return Connection(