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/repository/queries/template.sql

@@ -0,0 +1,22 @@
+-- name: ListTemplates :many
+SELECT id, scope, tenant_id, origin_type, template_key, template_name,
+       schema_json, prompt_template, prompt_visibility, card_config_json,
+       status, version_no, created_at, updated_at
+FROM article_templates
+WHERE (scope = 'platform' OR tenant_id = sqlc.arg(tenant_id)::bigint)
+  AND status = 'active' AND deleted_at IS NULL
+ORDER BY created_at DESC;
+
+-- name: GetTemplateByID :one
+SELECT id, scope, tenant_id, origin_type, template_key, template_name,
+       schema_json, prompt_template, prompt_visibility, protected_prompt_asset_key,
+       card_config_json, status, version_no, created_at, updated_at
+FROM article_templates
+WHERE id = sqlc.arg(id)
+  AND (scope = 'platform' OR tenant_id = sqlc.arg(tenant_id)::bigint)
+  AND deleted_at IS NULL;
+
+-- name: GetTemplateSchema :one
+SELECT id, template_name, schema_json
+FROM article_templates
+WHERE id = sqlc.arg(id) AND deleted_at IS NULL;