Use find_spec instead of try/except for htmx module discovery

The previous try/except ImportError approach would silently catch import
errors from within the htmx module itself, masking real bugs. Now we use
find_spec to check if the module exists before importing, allowing any
ImportError from within the module to propagate properly.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: mvazquez-kaiko

src/djhtmx/utils.py

@@ -1,4 +1,5 @@
 import importlib
+import importlib.util
 import pkgutil
 import typing as t
 from urllib.parse import urlparse
@@ -130,10 +131,10 @@ def autodiscover_htmx_modules():
     """
     for app_config in apps.get_app_configs():
         module_name = f"{app_config.module.__name__}.htmx"
-        try:
-            module = importlib.import_module(module_name)
-        except ImportError:
+        spec = importlib.util.find_spec(module_name)
+        if spec is None:
             continue
+        module = importlib.import_module(module_name)
         if hasattr(module, "__path__"):
             # If it's a package, recursively walk it importing all modules and packages.
             for info in pkgutil.walk_packages(module.__path__, prefix=module_name + "."):