refactor(tests): reorganize tests per module with shared root conftest

Move 42 single-module test files into app/modules/*/tests/ directories
while keeping 40 cross-module and infrastructure tests central in tests/.
Hub fixtures (engine, db, client, cleanup) moved to root conftest.py so
both tests/ and module tests inherit them. Update pyproject.toml testpaths
and Makefile TEST_PATHS to discover all test locations.

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

pyproject.toml

@@ -66,6 +66,7 @@ unfixable = []
 "models/database/base.py" = ["F401"]
 # Ignore specific rules in test files
 "tests/**/*.py" = ["S101", "PLR2004"]
+"app/modules/*/tests/**/*.py" = ["S101", "PLR2004"]
 # Alembic migrations can have longer lines and specific patterns
 "alembic/versions/*.py" = ["E501", "F401"]
 
@@ -113,7 +114,18 @@ ignore_errors = true
 # =============================================================================
 [tool.pytest.ini_options]
 minversion = "7.0"
-testpaths = ["tests"]
+testpaths = [
+    "tests",
+    "app/modules/tenancy/tests",
+    "app/modules/catalog/tests",
+    "app/modules/billing/tests",
+    "app/modules/messaging/tests",
+    "app/modules/orders/tests",
+    "app/modules/customers/tests",
+    "app/modules/marketplace/tests",
+    "app/modules/inventory/tests",
+    "app/modules/loyalty/tests",
+]
 python_files = ["test_*.py", "*_test.py"]
 python_classes = ["Test*"]
 python_functions = ["test_*"]