Catch InvalidVersion specifically in plugin update comparison

Address review feedback: the version comparison caught a blind `except
Exception` (ruff BLE001). Split the two failure modes and catch each
specifically — ImportError for a missing `packaging` (a core dependency)
and InvalidVersion for an unparseable version string — while preserving
the existing "surface the mismatch" fallback behavior. Added a test for
the unparseable-version path.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012EW8yDbsk8EceDpq6Hjgqj

web_interface/blueprints/api_v3.py

@@ -134,9 +134,15 @@ def _is_plugin_update_available(installed_version: str, latest_version: str) ->
     if installed_version == latest_version:
         return False
     try:
-        from packaging.version import parse as _parse_version
+        from packaging.version import parse as _parse_version, InvalidVersion
+    except ImportError:
+        # packaging is a core dependency, but if it's somehow unavailable we
+        # can't compare semantically — surface the mismatch we already know
+        # exists (the two strings differ).
+        return True
+    try:
         return _parse_version(latest_version) > _parse_version(installed_version)
-    except Exception:
+    except InvalidVersion:
         # Unparseable version string: we can't tell direction, so surface the
         # mismatch rather than silently hiding a potential update.
         return True