Validate timeout in Connection/AsyncConnection __init__

Cycle 8 — direct Connection(address, timeout=-1) / AsyncConnection
calls bypassed the dqlitedbapi.connect() validation added earlier
and silently stored invalid timeouts that caused hangs or stranger
downstream errors. Both class constructors now reject non-finite
and non-positive timeouts up front.

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

Author: antoineleclair

src/dqlitedbapi/aio/connection.py

@@ -23,8 +23,12 @@ def __init__(
         Args:
             address: Node address in "host:port" format
             database: Database name to open
-            timeout: Connection timeout in seconds
+            timeout: Connection timeout in seconds (positive, finite)
         """
+        import math
+
+        if not math.isfinite(timeout) or timeout <= 0:
+            raise ValueError(f"timeout must be a positive finite number, got {timeout}")
         self._address = address
         self._database = database
         self._timeout = timeout

src/dqlitedbapi/connection.py

@@ -70,8 +70,15 @@ def __init__(
         Args:
             address: Node address in "host:port" format
             database: Database name to open
-            timeout: Connection timeout in seconds
+            timeout: Connection timeout in seconds (must be positive
+                and finite; validated here so direct ``Connection(...)``
+                calls don't silently accept bad values that later
+                produce hangs or stranger downstream errors)
         """
+        import math
+
+        if not math.isfinite(timeout) or timeout <= 0:
+            raise ValueError(f"timeout must be a positive finite number, got {timeout}")
         self._address = address
         self._database = database
         self._timeout = timeout