feat(hosting,prospecting): add hosting unit tests and fix template bugs

- Add 55 unit tests for hosting module (hosted site service, client
  service service, stats service) with full fixture setup
- Fix table_empty_state macro: add x_message param for dynamic Alpine.js
  expressions rendered via x-text instead of server-side Jinja
- Fix hosting templates (sites, clients) using message= with Alpine
  expressions that rendered as literal text
- Fix prospecting templates (leads, scan-jobs, prospects) using
  nonexistent subtitle= param, migrated to x_message=
- Align hosting and prospecting admin templates with shared design system

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -160,6 +160,7 @@ testpaths = [
     "app/modules/monitoring/tests",
     "app/modules/analytics/tests",
     "app/modules/prospecting/tests",
+    "app/modules/hosting/tests",
 ]
 python_files = ["test_*.py", "*_test.py"]
 python_classes = ["Test*"]
@@ -223,6 +224,7 @@ markers = [
     "dev_tools: marks tests related to developer tools module",
     "analytics: marks tests related to analytics module",
     "prospecting: marks tests related to prospecting and lead generation module",
+    "hosting: marks tests related to hosting and POC website module",
     "inventory_module: marks tests related to inventory module",
     # Component markers
     "service: marks tests for service layer",