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/article_template.go

@@ -0,0 +1,21 @@
+package domain
+
+import "time"
+
+type ArticleTemplate struct {
+	ID                      int64
+	Scope                   string
+	TenantID                *int64
+	OriginType              string
+	TemplateKey             string
+	TemplateName            string
+	SchemaJSON              map[string]interface{}
+	PromptTemplate          *string
+	PromptVisibility        string
+	ProtectedPromptAssetKey *string
+	CardConfigJSON          map[string]interface{}
+	Status                  string
+	VersionNo               int
+	CreatedAt               time.Time
+	UpdatedAt               time.Time
+}