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/workspace.go

@@ -0,0 +1,31 @@
+package domain
+
+import "time"
+
+type WorkspaceOverview struct {
+	ArticleCount           int64 `json:"article_count"`
+	PublishedCount         int64 `json:"published_count"`
+	BrandCount             int64 `json:"brand_count"`
+	SupportedPlatformCount int   `json:"supported_platform_count"`
+}
+
+type RecentArticle struct {
+	ID             int64     `json:"id"`
+	Title          *string   `json:"title"`
+	TemplateName   *string   `json:"template_name"`
+	GenerateStatus string    `json:"generate_status"`
+	PublishStatus  string    `json:"publish_status"`
+	SourceType     string    `json:"source_type"`
+	WordCount      int       `json:"word_count"`
+	SourceLabel    *string   `json:"source_label"`
+	CreatedAt      time.Time `json:"created_at"`
+}
+
+type QuotaSummary struct {
+	PlanCode   string     `json:"plan_code"`
+	PlanName   string     `json:"plan_name"`
+	TotalQuota int        `json:"total_quota"`
+	UsedQuota  int        `json:"used_quota"`
+	Balance    int        `json:"balance"`
+	ResetAt    *time.Time `json:"reset_at"`
+}