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/shared/auth/claims.go

@@ -0,0 +1,12 @@
+package auth
+
+import (
+	"github.com/golang-jwt/jwt/v5"
+)
+
+type Claims struct {
+	UserID   int64  `json:"user_id"`
+	TenantID int64  `json:"tenant_id"`
+	Role     string `json:"role"`
+	jwt.RegisteredClaims
+}