feat(core): add core module with mixins, services, and background jobs

- Add Model Mixins: TimestampMixin, SoftDeleteMixin, AuditMixin, etc.
- Add Base Services: BaseService, BulkOperationsMixin, QueryOptimizerMixin
- Add Base ViewSets with bulk operations
- Add BackgroundJob model for Celery task tracking
- Add BaseAppCommand for management commands
- Add permissions, pagination, filters, cache, logging
- Migrate tests to factory_boy + faker
- Add CHANGELOG.md
- 297 tests passing

src/apps/core/middleware.py

@@ -0,0 +1,131 @@
+"""
+Core middleware components.
+
+Provides Request ID tracking and other cross-cutting concerns.
+"""
+
+import logging
+import threading
+import uuid
+
+from django.utils.deprecation import MiddlewareMixin
+
+logger = logging.getLogger(__name__)
+
+# Thread-local storage for request context
+_request_context = threading.local()
+
+
+def get_request_id() -> str | None:
+    """Get current request ID from thread-local storage."""
+    return getattr(_request_context, "request_id", None)
+
+
+def get_current_request():
+    """Get current request from thread-local storage."""
+    return getattr(_request_context, "request", None)
+
+
+class RequestIDMiddleware(MiddlewareMixin):
+    """
+    Middleware that generates or extracts a unique request ID for each request.
+
+    The request ID is:
+    1. Extracted from X-Request-ID header if present
+    2. Generated as UUID4 if not present
+    3. Added to response headers
+    4. Available via get_request_id() for logging
+
+    Usage in logging:
+        from apps.core.middleware import get_request_id
+        logger.info(f"[{get_request_id()}] Processing request")
+    """
+
+    REQUEST_ID_HEADER = "X-Request-ID"
+
+    def process_request(self, request):
+        """Extract or generate request ID and store in thread-local."""
+        request_id = request.headers.get(self.REQUEST_ID_HEADER)
+
+        if not request_id:
+            request_id = str(uuid.uuid4())
+
+        request.request_id = request_id
+        _request_context.request_id = request_id
+        _request_context.request = request
+
+        return None
+
+    def process_response(self, request, response):
+        """Add request ID to response headers."""
+        request_id = getattr(request, "request_id", None)
+        if request_id:
+            response[self.REQUEST_ID_HEADER] = request_id
+
+        # Clean up thread-local storage
+        _request_context.request_id = None
+        _request_context.request = None
+
+        return response
+
+    def process_exception(self, request, exception):
+        """Log exception with request ID."""
+        request_id = getattr(request, "request_id", "unknown")
+        logger.error(f"[{request_id}] Unhandled exception: {exception}")
+        return None
+
+
+class RequestLoggingMiddleware(MiddlewareMixin):
+    """
+    Middleware for logging request/response details.
+
+    Logs:
+    - Request method, path, and request ID
+    - Response status code and timing (if available)
+    """
+
+    def process_request(self, request):
+        """Log incoming request."""
+        import time
+
+        request._start_time = time.time()
+        request_id = getattr(request, "request_id", "N/A")
+
+        logger.info(
+            f"[{request_id}] {request.method} {request.path} - Started",
+            extra={
+                "request_id": request_id,
+                "method": request.method,
+                "path": request.path,
+                "user": getattr(request.user, "id", None)
+                if hasattr(request, "user")
+                else None,
+            },
+        )
+        return None
+
+    def process_response(self, request, response):
+        """Log response details."""
+        import time
+
+        duration = None
+        if hasattr(request, "_start_time"):
+            duration = time.time() - request._start_time
+
+        request_id = getattr(request, "request_id", "N/A")
+
+        logger.info(
+            f"[{request_id}] {request.method} {request.path} - "
+            f"{response.status_code} ({duration:.3f}s)"
+            if duration
+            else f"[{request_id}] {request.method} {request.path} - "
+            f"{response.status_code}",
+            extra={
+                "request_id": request_id,
+                "method": request.method,
+                "path": request.path,
+                "status_code": response.status_code,
+                "duration": duration,
+            },
+        )
+        return response