feat: add tenant and user management with migrations, handlers, and tests

- Implemented tenant and user management features including:
  - Tenant creation and management with associated migrations.
  - User creation and management with associated migrations.
  - Tenant membership management with associated migrations.
  - Platform user roles management with associated migrations.
  - Quota management with associated migrations.
  - Article and template management with associated migrations.
- Added HTTP handlers for templates and workspaces.
- Created tests for protected and public routes.
- Introduced a script to check tenant scope in SQL queries.
- Documented task plan for backend completion and frontend foundation.

server/internal/tenant/domain/competitor.go

@@ -0,0 +1,18 @@
+package domain
+
+import (
+	"encoding/json"
+	"time"
+)
+
+type Competitor struct {
+	ID               int64
+	TenantID         int64
+	BrandID          int64
+	Name             string
+	Website          *string
+	Description      *string
+	ProductLinesJSON json.RawMessage
+	CreatedAt        time.Time
+	UpdatedAt        time.Time
+}